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Home My WebLink AboutAPA32TK. 1425 .S8 A23 no.32 I DATE DUE ~ I ~-" .DEMCO 38-297 --;- ALASKA POWER AUTHORITY SUSITNA HYDROELECTRIC PROJECT TASK 3 -HYDROLOGY ICE OBSERVATIONS 1980 -81 AUGUST 1981 Prepared for: ACRES AMERICAN INCORPORATED 1000 Liberty Bank Building Main at Court Buffalo,New York 14202 Telephone (716)853~7525 Prepared by: R&M CONSULTANTS,INC. 5024 Cordova Street Anchorage,Alaska 99502 Telephone:(907)279-0483 ,'.Y o 1 ,t;~Ul TK ?S S~ A~- no ,~ ALASKA POWER AUTHORITY SUSITNA HYDROELECTRIC PROJECT TASK 3 -HYDROLOGY ICE OBSERVATIONS -1980-81 TABLE OF CONTENTS PAGE LIST OF TABLES iii LIST OF FIGURES iv LIST OF PLATES v SUMMARY vi 1 -INTRODUCTION 1-1 1.1 -Field Study 1-1 1.2 -Review of AvailabIe Information 1-1 2 -CLIMATE CONDITIONS DURING THE WINTER OF 2-1 1980-81 FOR SOUTHCENTRAL ALASKA 2.1 -Air Temperatures 2-1 2.2 -Precipitation 2-2 3 -ICE THICKNESS 3-1 4 -CHRONOLOGY OF FREEZEUP AND BREAKUP EVENTS 4-1 ON THE SUSITNA RIVER 4.1 -Freezeup Observations 4-1 (a)Review of Historical Data (b)1980 Freezeup Observations 4.2 -Breakup Observations (a)Review of Historical Records (b)1981 Breakup Observations 5 -REFERENCES -j- s7/ff2 4-1 4-1 4-10 4-10 4-12 5-1 ALASKA POWER AUTHORITY SUSITNA HYDROELECTRIC PROJECT TASK 3 -HYDROLOGY ICE OBSERVATIONS -1980-81 TABLE OF CONTENTS ATTACHMENT A -CLIMATOLOGICAL DATA FOR TALKEETNA ALASKA PROVIDED BY THE NATIONAL WEATHER SERVICE ATTACHMENT B -STREAMFLOW RECORDS FOR THE SUSITNA RIVER PROVIDED BY THE U.S.GEOLOGICAL SURVEY ATTACHMENT C -SUMMARY OF BREAKUP OBSERVATIONS DURING 1981 ON THE LOWER SUSITNA RIVER AT THE DESHKA -SUSITNA RIVER CONFLUENCE PLATES -ii- 57/ff3 LIST OF TABLES - Number 3.1 3.2 3.3 4.1 4.2 4.3 4.4 4.5 4.6 4.7 s7/ff4 Title Susitna River Ice Thickness Measurements Historic Record of Ice Thickness Measurements on the Susitna River at Gold Creek &Cantwell (Vee site) Historic Record of Ice Thickness Measurements on the Susitna River at Tal keetna &Trapper Creek Occurrence of Ice at Sel,ected Susitna River Sites,Dates Provided by the USGS Water Temperature Records during Freezeup (11980)on the Susitna iRiver Ice Cover Progression on the Susitna River - Field Observations Field Measurements of Water Surface Profiles on the Susitna River in the Vicinity of Chase Field Measurements of Water Surfaces Profiles on the Susitna River near Cross-Section 29 National Weather Service Summary of Breakup Events on the Susitna &Talkeetna Rivers Susitna River Breakup Observations (1980) Water Su rface Elevations -iii - 3-2 3-6 3-9 4-17 4-18 4-19 4-20 4-21 4-22 4-27 LIST OF FIGURES Number 2.1 4.1 4.2 4.3 4.4 4.5 s7/ff5 Title Average Monthly Air Temperatures at Talkeetna:Historical versus 1980-81 Ice Cover Progression on the Susitna River above the Susitna-Chulitna Confluence Water Surface Profiles on the Susitna River in the Vicinity of Chase Water Surface Profiles on the Susitna River near Cross-section 29 Water Surface Profiles on the Susitna River in the Vicinity of Gold Creek Water Surface Profiles on the Susitna River in the Vicinity of Curry -iv- 2-3 4-28 4-29 4-30 4-31 4-32 LIST OF PLATES Number 1-7 8-14 15-18 57/ff6 Description Summary of river ice conditions on the Susitna River from the Parks Hwy.Bridge to Watana Creek,October 11 -November 13,1980. Summary of river ice conditions on the Susitna River fr:om the Parks Hwy Bridge to Watana Creek,November 29 -December 12,1980. Summary of ice conditions on the Susitna River from the Parks Hwy.Bridge to the Indian River,April 23 -May 8,1981. -v- SUMMARY The river ice conditions observed through the winter of 1980-1981 on the Susitna River are summarized in this report to provide description and data needed in further studies of the feasibility of hydropower development on the river.Emphasis in the ice studies was placed on the river reach from Tal keetna to Portage Creek since it was felt this reach would be most affected by proposed project development. Climate conditions in the Susitna Basin varied significantly from normal during the study period,influencing the processes of ice cover formation and breakup on the river.In early December,as the ice cover was forming on the Susitna,ai r temperatures were well below no'rmal.This was followed by unusually warm air temperatures in January after the ice cover had formed over the length of the river.During these early winter months,precipita- tion was low.Snow survey data showed that the snowpack in the Susitna Basin was 30-50%below normal th rough January.The combination of these factors resulted in an average ice thickness of 2.5 feet on the Susitna River at Gold Creek in January,close to the historical average at that site. Beginning of the freezeup process on the Susitna River could be given as October 11 &12 when frazil ice was first observed flow- ing in the river and water temperatures dropped to 32°F.How- ever,formation of an ice cover did not begin until mid November. At that time an ice cover was forming on the river upstream from the confluence of Watana Creek.On November 11,the ice cover extended approximately 6 miles above Watana Creek. In the river downstream of Devil Canyon,an ice cover did not begin to develop unti I early December.On November 29,an ice bridge was observed in the Susitna River at Tal keetna,but the river upstream to Portage Creek had not begun forming an ice cover. However,on December 1,the Susitna -Chulitna confluence was bridged and an ice cover extended approximately six miles up- stream on the Susitna.Over the next two weeks,ice cover growth progressed at an average rate of 2.7 miles per day in the river between the confluence and Portage Creek.The ice cover formation process raised the water level 2 to 4 feet through this reach. By December 15,the river was ice covered from the confluence upstream into Devil Canyon.Open water persisted in several turbulent reaches from Devil Canyon up to Devil Creek through the month of December.Throughout the length of the river, -vi- 57/ff7 several open leads persisted through the winter.Some of these were velocity leads in the main channel thalweg,others seemed related to groundwater inflow into the river. The cover began to deteriorate in March due to unusually warm air temperatures.There was no significant precipitation during early spring to increase runoff in the watershed.Therefore,river discharge did not increase sufficiently to create strong forces on the ice cover and initiate breakup.Instead,the ice began to disintegrate in place with long open leads developing through the length of the river.An early breakup was predicted for the Susitna River.A return to near normal air temperatures in April and May slowed the breakup processes occurring in the basin. By May 1,there were obvious signs that the ice had undergone first movement.Over the next week,condition of the ice cover deteriorated.Ice jams formed at several locations between Talkeetna and Portage Creek as the ice cover broke and began moving downstream.However,breakup was relatively mild due to the minimal to nonexistent snowpack left in the basin by the end of April and the deteriorating condition of the river ice.There were no major changes in the river channel configuration on sig- nificant scouring of the river banks due to ice movement.Scar- ring of trees by ice movement was noticed in a few locations,most dramatically in the vicinity of Cross Section 7,after release of the ice jam at the confluence. By May 9,the main channel from Tal keetna upstream was ice free, but remnant ice was stranded on shore or packed into side chan- nels.Over the following weeks,risIng water levels flushed out the remaining ice or it melted in place. Overall,the timing of breakup on the Susitna was near normal based on limited historical records. -vii- s7/ff8 1 -INTRODUCTION This report provides a summary of freezeup,winter and breakup ice observations carried out by R&M Consultants,Inc.during the winter of 1980-81 on the Susitna River and a review of limited historical records on river ice conditions. 1.1 -Field Study The field program was designed to provide description and data needed in analyses and assessment of hydroelectric development in the Upper Susitna River on ice cover and water level regime downstream of the proposed project site.Emphasis in field studies was placed on the river downstream from Devil Canyon to Tal keetna,since it was felt that this reach would be most affected by project development. Observations and measu rements made in the field basically included the following: o o o o o nature and timing of ice cover development field documentation and interpretation of freeze-up processes measurement of various hydraulic parameters at critical sections documentation of winter ice cover conditions Field documentation and interpretation of ice cover deterioration during the spring,including location and natu re of ice jams Supporting data on water temperatu res,climate records from Talkeetna,snow pack throughout the Susitna Basin and streamflow at Gold Creek during key times of the year are also included. 1.2 -Review of Available Information Very limited records are available for the Susitna River basin relating to river ice regime.However,several agencies were very helpful in gathering the available data,especially the Alaska Railroad,National Weather Service River Forecast Center and the U.S.Geological Su rvey Water Resources Division. The data provided are presented in various tables and appendices within the report and provide comparison of the nature of freezeup and breakup on the Susitna River in the past with events observed during the winter of 1980-81. s7/aa 1-1 2 -CLIMATE CONDITIONS DURING THE WINTER OF 1980-81 FOR SOUTHCENTRAL ALASKA Climate conditions in Southcentral Alaska during the winter of 1980-81 varied dramatically from normal,influencing rates of ice cover development during freezeup and the nature of breakup on the Susitna River. 2.1 -Air Temperatures Figure 2.1 shows the average·monthly air temperatures at Talkeetna for October 1980 to May 1981 versus the historical averages at Tal keetna.The data for this table were taken from NOAA reports which are included as Attachment A. Freezeup:The most notable deviations in ai'r temperatures occurred during December and January.During the key period of ice cover formation on the Susitna River in early December average air temperatures were more than 13 degrees below normal at Tal keetna.This would tend to accelerate the formation of an ice cover on the Susitna River.Daily readings of maximum and minimum air temperatures at Tal keetna are included in Attachment A. The below-normal December temperatures were followed by unusually warm air temperatures dur,ing January which reduced the lower elevation snowpack to a minimum in most of the southcentral region.Above average streamflow at Gold Creek also reflects the warmer air temperatures and runoff from melting of the early winter snowpack. More detailed discussion of thle influence of ai r temperatures on the freezeup process and winter conditions is included in following sections. Breakup:In the spring,warmer-than-normal air temperatures during March with no substantial precipitation resulted in a gradual decrease in the already low snowpack for the Lower Susitna Valley,reducing the potential for a severe breakup on the Susitna River.During late March,the NWS predicted breakup one to three weeks earlier than usual. Air temperatures returned to nearly normal for April and May resulting in a return to near normal timing for breakup on the Susitna River. s7/cc 2-1 2.2 -Precipitation Early winter was unusually dry in the Susitna Valley area. Precipitation records at Tal keetna from the National Weather Service show precipitation at 85%of normal for October,60%of normal for November and approximately 33%of normal for December. Snow survey data from the Soil Conservation Service (SCS)shows a continuation of this trend through January.Many snow courses in the Southcentral area showed a new minimum snow depth. Precipitation was 20-40%below normal in the region and unusually warm air temperatures during the month reduced snowpack at lower elevations to 50%below normal.High elevation sites in the Susitna Basin were closer to normal,with overall snowpack in the Upper Susitna about 30%below normal. Snowfall during February and March was normal based on SCS records.However,snowpack in the Lower Susitna Basin and valley bottoms of the Upper Susitna Basin remained well below average.The snowpack approached normal with increased elevation.Unusually warm air temperatures during March further reduced the snowpack.Valley floors and lower elevation sites showed very lean to nonexistent snow cover by the end of March. South of the Alaska Range,precipitiation during April was one-fourth to one-half the normal amount.By the end of April, the snowpack below 3,000 feet was gone or rapidly melting. Overall,snowpack at the lower elevation sites and on the valley floors in the upper basin was 40-70%of normal.Portions of the Talkeetna and Alaska Ranges were near average,but the rest, especially the western portion of the Tal keetna Mountains,were well below average for the year. s7/cc 2-2 "+-+-ij-+-+-+-+-t-+-t--JH-+-t-+-+-++-t-+-H-++-++-H I;\!'L I !_I :_(;..,_-.. +-+-+-1--++-1-+-+-+-+-1--++-1-+--,--+1-+-t-+--t--'-+-+-t-~H ..I '".I:,-..f ~.~""-Jl-+-+--l--I-+-H-++-+-.j-t-+-H-+-+-+-+-t-+-+-1f-t-+-+-+-t1:......-:--,:_ir :..",",,"··, ' , .Ii'.1\'/'"IA!.,..:/~rlr:-r,.-VII'I .....i II ,~""",1 ~ .:-! 111) I .., l-+--H-+-+-+-+,-+-c,:I-+-+-t-+--H-+-+-+-+-t-+--H-+-+-+-+-t-++-1-+-+-+-+--t-+--H-+-+-+-+-t-++..t-Ti'+-l-+-+-+-+-t-+--H-+--ft+-I-t-I--+-I-+-+-+-++ -+-+-+-+-I--++-t-+-+-+-+-t-+--t-+-+-+-,+-t-+-+-+-+-t--;-+-I-+-+-+-+-t-+-+-+-+-+-'-..-It-i-++-I-+-+-t--+-I--++-I-+-~-+-t-+--H-I-+-++I60.-t-+++++++++++++++++-+-t-f-t-f-+-JH-I--t-H-H-++++++ll-+++++-+-+-H-t-i-t--'r-+-H---M-+-+++++-t-+Ir.+-f-+-t-l--+-li-++-t-l-t-I--+-Ii-++-+-I-t-I--H-+-+-+-I-t-I--H-+-+-+-I-t-I--','.'-+f-l--t-+-t-+-+-+-+-t-+-H-+-+-+-+-,ol-+-+-f-+-+-+-+-t-I I !;r-+-t-++-t-l-t--+-+-t-l-t-++-t-l-t-++-t-l-I--++,-t--1-+-t-I-+-I-+-t--+--H-+-t-+--H-t-'T-+I+---H-+-"-++-1-+-+-+,-+--JH-++-t--lr-.T++-t-lH-++I ,-t-++-tH--+-t-+-t-++-tH--+-t-l-t-++-l---;-+-t-l-t-++-l-+-+-+--+-"".,_t-J-++-t-+-+-+-+-~+-t-+-+-+-t--t-++-tf-+-+-t-+-t-I-+-tf-+-++, ~"""i'++-1H--t-+-+-t-+'+-1-+-+-+-+-t-+--Hr+-+-+-I-,..-++-l-+-+-+-I-+-++-l-+-+--<- -4 t{:r-: ...ynut-H-+-H-++++-H-+-t-+-t-+++-H-+-H-++++-+-t-+-I-'---.-.+1t-fH-+-H-++++-t-i-+-+-+-+++-+-H'H-+-t-+++-+-t-i1-I ~. :-lG--t-If-t-+-t-+-t-+-t-lf-t-+-t-++-+-t-lf-t-+-+-++-+-t-lf-t-+-t+H·-t-lf-··--j-+Ht-+-t-+-Hc--f--H-++-+-+--1H-+-t-++-+-+-H--H-+H-t-t-1 '--->.1........._"..I.',,,-rtt::n\ltt~:ttt=tt:t:t'::ttttt:ttt=t=tt:t~~:t==t:$!~xttt:tt:t'::tttt4:ttt:t:t,t!::ttt=dttti=ttt I,..........::,\I -+-t-+4-i-+-.L.-t--t--H+t-+--f,-++-+-+-I-+-H-++-+-+-t-1t-1\3c,.,i ~\,II'N-f---,-';---r-.+\Hf-'/--;-.-+--l-t-....-+-+-++-I'-+;;;,++-+-+-,+-+-+-HT+-I'-+-!.H~+-+-+--i-i--~,-+-+-+-+--1f-+,+-t-++-+-+-H--H;-++-+-+-t-+-H-+I , I 1::11 I 'i, i Ii; lJA ~.++-++'++++-t-+++-++,++++-ttt++++-W-++,++-lII',++++++++++++++++=I-+++++-++-++-++-++-++-++-+-+I ft'2B--H-+-++++~~'+-+'-H-Hf-++-+++-+-H-t-+'+-:l1Ll--++.,..-t-H-l.-~-H-+-H-++-H---!-+---+--t--'--HH-.l--.+-+-+-+-H-+++It!I A ..__~-+-,-i -j-.;--+-4--+--1-'-,++~H--H-++-r!H-H-..l.'+yi..-'fl.L..j-l-.;+-+-+-..-+..:.;-+-4-..:.....j-:""H,-+-~i++-+-4----1,H-'+--+-+-H--H-++-++--H --, :OVERAL'-AVERAGE:r-HH-i-H--t---+-H-H-H--t+-t-f.-H-Irt-H-+-:-j--j-,HiH-i--t-'--+-+~---j..o.+-++-+HMON TL Y TEMPERA TVleE, 0'1 N o J F M A MONTHS M I v A PREPARED BY I PREPARED FOR' .~.;~':.~~.. .,',J-{~~.,>....•.....:.'":;", R&M CONSULTANTS,INC. 3 •ICE THICKNESS Ice thickness measurements were carried out through the winter at numerous sites from Chase to Vee Canyon often in connection with winter discharge measurements or river channel cross section surveying. Table 3.1 lists results from field measurements made by R&M Consultants,Inc.during the winter of 1980-81.At each site, average ice thickness was calculated from field notes and maximum and minimum thicknesses were listed to indicate the range of values observed.Where available,comments on the characteristics of the ice were included. Ice thicknesses at Gold Creek since 1950,as reported by Bilello (1980)are shown in Table 3.2.Records at this site are most complete and allow best comparison of historical ice thicknesses with observed values for 1981.January and February measure- ments of maximum and minimum thicknesses for 1981 appear to be below the historical average for that time of year.Unusually warm January temperatures slowed the ice growth at Gold Creek. An additional table extracted from Bilello (1980),Table 3.3,sihows ice thickness through the winter months on the Susitna River at Talkeetna and Trapper Creek from 1961 to 1972.Though we have no comparative ice thicknesses for the winter of 1980-81 at Talkeetna,dates for first ice,freeze over of the channel or breakup of the ice cover can be used along with climatic and streamflow data to rna e comparisons with timing of similar events for the winter of 1980-81,and expected rates of ice cover thickening and deterioration. susi7/ee 3-1 susi7/dd1 TABLE 3.1 SUSITNA RIVER ICE THICKNESS Snow Cover River Ice Thickness (ft.)Number of on Ice Site Location Date Width Avera~Maximum Minimum Observations (ft.)Comments Vee Canyon 1-13-81 353 6.3 *10.0 3.1 11 3 holes drilled with ice 10 feet thick,auger not long enough to penetrate ice cover.Several overflow layers. Deadman Creek 2-27-81 327 6.1 6.3 6.0 3 0.7 Right channel CSR (URX 101)4-4-81 366 1.6 2.6 0.8 4 Right channel 410 4.1 4.4 3.8 6 Left channel URX 102 3-4-81 313 2.3 3.1 1.8 6 w URX 103 3-4-81 1370 2.5 4.6 1.0 16 I tv 2.0 10URX1043-5-81 616 4.1 5.8 URX 105 3-5-81 417 2.9 4.6 0.2 9 URX 106 (3-26-81) 3-6-81 431 2.5 5.8 1.4 9 Watana Dam 2-27-81 165 4.5 5.4 3.5 6 0.5 CSR URX 107 3-6-81 290 4.7 5.6 2.3 8 Watana Damsite 2-27-81 160 4.4 5.0 4.3 3 0.5 Significant dip in ice at center URX-l07A 3-6-81 423 4.0 4.8 1.4 10 *Assumed ice thickness of 10.0 feet for three center holes in channel to calculate average. susi]/dd2 TABLE 3.1 (Continued) Snow Cover River Ice Thickness (ft.)Number of on Ice Site Location Date Width Average Maximum Minimum Observations (ft.)Comments URX-108 3-7-81 382 3.8 5.5 1.2 9 URX-108A 3-7-81 435 3.8 4.5 2.5 10 W.Q.Monitor 2-24-81 460 4.4 5.2 3.6 4 0.6 URX-109 3-7-81 605 3.8 4.8 2.5 10 Ice predominantly black ice (80%,90%) URX-110 3-8-81 168 2.9 4.7 0.3 4 Left channel,frozen to the bed, all black ice 3-8-81 340 2.8 4.0 0.4 8 Center channel strong flow underpressure along left side 3-8-81 238 2.6 4.1 0.4 6 Right channel w 3-8-81 2.75 Overall average ice thicknessIw Watana Streamgage (URX-111)4-1-81 400 3.0 4.2 2.1 16 URX-112 3-8-81 260 1.8 3.5 0 7 Open lead 80 1 from R/B,20 1 wide URX-113 3-9:-81 464 4.3 5.2 3.3 10 URX-114 3-9-81 336 2.9 4.0 0.4 ]Left channel,low flow 3-9-81 512 3.7 4.7 2.5 9 Right channel =Main channel Two small side channels run on far sides of floodplain URX-115 3-10-81 502 4.0 4.7 2.5 10 Average snowice =0.8 1 ,rest black ice,flow under pressure along LIB susi7/dd3 TABLE 3.1 (Continued) Snow Cover River Ice Thickness (ft.)Number of on Ice Site Location Date Width Average Maximum Minimum Observations (ft.)Comments URX-116 3-11-81 408 4.3 6.8 1.3 9 URX-117 3-11-81 638 2.2 4.1 0.3 14 Gravel bar in mid-channel,thick ice along steep RIB URX-118 3-11-81 464 3.3 5.0 0.4 10 Main channel,average snow ice =0.5 1 3-11-81 173 1.2 1.8 0.2 3 URX-119 3-12-81 507 3.3 5.1 2.0 10 Maximum thickness along steep RIB URX-120 3-12-81 513 2.4 4.2 0.3 10 Average snow ice =0.5' Near Devil w Creek I URX -121 3-13-81 351 1.8 3.9 0.2 6,c:. Upper D.C. CSR 3-5-81 202 3.1 3.2 3.0 3 0.3 Devil Canyon 4-13 14.6 23.0 Ice shelf-not ice cover thickness,see R&M preliminary study Portage Creek 3-5-81 166 3.0 3.7 2.4 7 1.0 Gold Creek 12-12-80 350 I ce cover formed through this reach 1-14-81 340 2.5 3.1 2.1 13 2-27-81 311 2.9 3.2 2.3 6 1.1 Ice very soft,open water and slush along LIB .Al I J1 susi7/dd4 TABLE 3.1 (Continued) Snow Cover River Ice Thickness (ft.)Number of on Ice Site Location Date Width Avera~Maximum Minimum Observations (ft.)Comments Sherman CSR 3-5-81 525 2.4 2.7 2.1 3 2.9 Holes drilled 1200'D/S from crest gage Curry CSR LRX-24 2-27-81 400 2.7 3.7 1.8 7 1.8 Chase CSR LRX-9 3-5-81 460 3.7 4.4 2.5 3 2.5 susi7/dd5 TABLE 3.2 ICE THICKNESS HISTORIC RECORD AT GOLD CREEK AND CANTWELL Snow Cover River Ice Thickness (ft.)Number of on Ice Site Location Date Width Average Maximum Minimum Observations (ft.)Comments Gold Creek 3-18-50 210 3.9 2.1 12-28-50 80 3.2 1.3 2-21-51 95 4.2 2.1 4-1-52 360 4.2 1.9 3-18-53 332 3.9 1.1 12-19-53 299 3.4 0.4*- w 2-11-54 472 4.6 2.0I (J'I 3-30-54 424 4.8 3.4 4-24-55 360 4.3 1.6 1-5-56 155 4.6 1.9 4-17-56 130 4.1 1.5 3-15-61 310 4.0 1.5 1-4-63 -3.1 2.3 2-20-63 -4.6 3.0 4-5-63 220 5.7*3.4 12-23-63 -3.4 1.5 *Historical maximum and minimum ice thicknesses susi7/dd6 TABLE 3.2 (Continued) Snow Cover River Ice Thickness (ft.)Number of on Ice Site Location Date Width Average Maximum Minimum Observations (ft.)Comments Gold Creek 2-19-64 270 3.7 1.8 (Continued) 1-12-65 170 3.8 1.6 1-19-67 130 2.8 2.3 4-8-67 155 3.9 2.7 4-15-69 582 4.2 1.6 4-1-70 290 3.8 2.5 1-14-81 340 2.5 3.1 2.1 13 w 2-27-81 311 2.9 3.2 2.3 6 1.1 I -.....J susi7/dd7 TABLE 3.2 (Continued) Snow Cover River Ice Thickness (ft.)Number of on Ice Site Location Date Width Average Maximum Minimum Observations (ft.)Comments-- Cantwell 4-10-62 320 4.7 0.6 Site assumed to be USGS sampling site "S us itna River near Cantwelfl'. 1-7-63 3.8 1.3 2-19-63 4.0 1.5 4-4-63 220 3.2 1.8 5-2-63 290 2.7 2.1 12-23-63 100 3.2 1.1 w 3-12-64 220 4.3 2.6 I 00 2-8-65 2.72504.2 1-21-67 280 5.3 3.0 3-28-67 80 5.2 2.3 3-23-70 212 4.2 3.1 1-13-81 353 6.3 10.0 3.1 ~Mile DiS of USGS cableway. Measure by R&M. River width determination not explained in table or text F" ,.qSLE 3.3 J!/sroIUC R.EcoRbSOF /c£r-vfCkN£SS /'1E.liSt.lREIIofGNTS ON THE StiS/7NI9 RIVER AT rl9~kE.TI'I/A *' TAI.Ja:i:IllA Meuu:r.,."lIts II\&4e on Susitoa RiVel' Date l:ov.II ;:ov.18 ;lOY.25 llee.30 Jan.2:7 teb.24 Mar.10 ;·iar.31 Mr.7 ~r.28 '·~5 1·:"7 25 Date Oct.2;' !lOY.2fo Cee.26 J ...,.30 .fe'.>.6 ieb.2:7 j·M.27 Apl'.3 Apr.10 IVr.30 1~1-19E2 ",iebess (inc"'.) ::0 ice 4.0 6.0 36.0 36.0 42.0 61.0 51.0 48.0 ll.O 2.0 River 0P~Q 1964-196:1 "'iekne.s (incbes) Shol'e ice 8.0 23.0 3ll.0 38.0 32.0 2$.0 22.0 18.0 Cllan~el ~:> ;:at" Oet::"1~ Nov.10 lIov.30 Ja'$'l.II rell.1 reb.22 Mar.~ A~r.2E Hay 3 t1e.:r15 :late ~t.11 :;C+,.30 !fov.20 "OV'.2:7 Ae.25 Jan.l~ Ja=..2? rell.zr Ifw'.2'5 Ar-r.~ ~.30 M&;'21 1c(2-1<;(.!' ",iekness (helles) first iee 7ree:te O·...er 4.0 33.0 33.5 24.0 43.5 V-.5 44.0 !c~rrce .~", 1965=IZ.e ';"llie:",".(t,elles) ;1rst iee 2/:'•'x1!Me ()'\-eT' 7.':) ::J..':J 16.0 20.0 l~.C 1'.l.:I 20.0 1~.0 !~~O:ce O"~ Jate lIov.e 1/"".22 }lOY.2~ Dee.2e J&.'.2~ 'teb.1', Mar.14 1'1u.21 Apr 25 Dat" ':c:-';.22 ~et.29 I'ee.3-24 :lee.31- ~L.".28 re'='.2~ Mar.25 ;"1'.22 ;'')r.2 0 /."J't'.30 W3-1064 'i"h 10'<.."0$$(inches) So:':'e l..:e 4.5 ~.O 32.0 2'5.0 33.0 38.0 . 34.0 ;0.0 190'6-1967 T.lloJo:ness (inehes) First ice freeze over Ch.a.."mel o:;>e:1 4.5 13.0 23.0 21\.0 25.0 21.5 ::::ce ·)rea.~1.:lb:up, 1RAPl'£J!'~:::=::::: :(e.....trf:""e"...~"..~,c O~''.l..Sit~&21.ve" ole..27 reb.3 Fe'>.21. M4:'.30 ;.;;:-.20 lte.;r 4 ~ll Date ~,-21- ~OV.28 tee.26J"".30 lebo 2:7 ;.l&:r.20 ::.or.'Z! !"6r-l 9€B 33.0 37.0 3£.0 30.0 20_0 C'pe~~U:' Ice.j""",l-rote 1970-1;'71 7hlc!~ne:::s (in":':'les; Ice J&3!: 2.0 15.0 30.0 30.0 3~.0 )2.0 '. !lOY.:0 :lee.S ~c.2~ r",>.1 re!:.22 f2r.~ Apr.1" .;pr.~ ~:ct.13 b1"v.1= N~."". Pee.13 Jan.1 Jfo/l.15roo.5 Feb.2f' l%B-l<M tee j ...,..1.-" 4.0 . ~L!..O 30.0 33.5 2h.C 16;0 Ic::e t'r~~'":lng UIl i971-127? .....~i~~:....!'~s (l"lc1"ee),1:"'.Ie'! fr!eze ('o~ 1,.:1 '::,,0 l~.n 21.0 23.0 ;').0 :ec_.-20 :lee.'2"'1 Ja".1:1 J ....31 Mar.- Mar.21 Mar.2~ ~.11 Apr.~ Apr.2~ 1%9-19?S 2.0 4.0 12.0 <:.0 28.0 32.0 27.0 25.0 Ice 't:'eaki~up ~an~el o;,e:'linz u.p 3-9 4 -CHRONOLOGY OF FREEZEUP AND BREAKUP EVENTS ON THE SUSITNA RIVER 4.1 -Freezeup (a)Review of Historical Data Limited information has been found on the nature and timing of freezeup processes for the Susitna River.Based on con- versations with personnel from the Alaska Railroad,over the past 20 years there has been no serious flooding or ice jam- ming related to ice cover development on the Susitna River. As a result,they have kept no records of first occurrence of frazil ice in the river or dates for ice cover formation at key locations.However,the USGS -Water Resources Division has provided freezeup dates for selected sites in the Susitna Basin based on field observations over the past few years. These are listed in Table 4.1.The range of dates note only the first occurrence of ice at gaging stations and may not truly reflect the ice regime within a particular river reach. Table 3.3 showing ice thickness measurements from the Susitna River at Tal keetna and Trapper Creek gives further definition to the timing of certain freezup events. No other information pertaining directly to freezeup processes for the Susitna River has been found. (b)1980 Freezeup In conjunction with ongoing river channel surveys during the Fall of 1980,records were kept on changes in water tempera- ture for the Tal keetna and Susitna Rivers,growth of shore ice,occurrence of anchor ice and first appearance of frazil ice in the river below Devil Canyon. On October 11,frazi I ice was fj rst observed in the Susitna River.By early afternoon,the leading edge of frazi I ice reached as far as River Mile 112.Areal coverage was 5 ...10% overall,with concentration of frazil flowing in the main chan- nel thalweg.The small slush floes were of relatively low density,lacking any cohesive strength. Farther upstream,in the vicinity of Gold Creek,areal cov- erage of frazil ice in the main channel was estimated to be 40%,again with ice concentrated in the main channel thalweg. In this reach J ice accumulated into larger floes up to 5 feet long,which appeared to be more buoyant due to thickening of the sluch floes.It appeared that frazil was being generated primarily through Devil Canyon and transported downstream in the main channel. 55/s 4-1 s5/s Table 4.2 shows water temperatures measured along the Susitna and Tal keetna Rivers during the early stages of freezeu p.Note,that on October 11th water tem peratu res of 34°F were recorded in the Susitna River at Talkeetna and near LRX-16 (RM 112.3)where frazit was observed in the afternoon. The following morning,October 12,the frazil ice front on the Susitna had reached Tal keetna,where water temperatu res now measured 32°F. At this time,there were no signs of frazil or shore ice devel- oping in the Chulitna or Tal keetna Rivers.Both appeared totally ice free. By late afternoon on October 12th,the leading front of frazil ice was approximately 5 miles above the Kashwitna River confluence (approximately RM 66).Frazil ice was flowing in the Yentna River,but no ice was observed in the Desh ka (K roto Creek). Frazil ice coverage in the main channel of the Susitna aver- aged 30%in the river above Tal keetna.Floes were beginning to accumulate at natural constrictions and in low velocity areas.Shore ice was also beginning to form in the quiet-water areas,but there was no significant constriction of the main channel due to shore ice growth. The following day,October 13th,first frazil ice was observed in the Talkeetna River,but there was still no sign of frazil ice flowing in the Chulitna River.I ce floes in the Susitna River above the Chulitna-Susitna confluence were more con- centrated,with coverage in the main channel estimated at 80%.Size of the floes varied from 2-5 feet in diameter through more turbulent reaches to 50-100 feet long in the constrictions below Curry and Portage Creek confluence. Shore ice growth was beginning to constrict the main channel in low velocity areas and to block the entrances of some side channels thereby restricting flow.Thin ice cover had formed on some quiet-water sloughs and side channels.Tributaries upstream from the Susitna-Chulitna confluence showed no signs of flowing frazil ice. For the rest of October,climatic conditions in the Susitna Valley caused daily variations in the concentration and strength of ice floes in the Susitna River.Shore ice growth continued to restrict flow in the main channel and block the entrance and exit to many side channels.These side chan- nels were also beginning to form an ice cover. 4-2 s5/s On October 31st,anchor ice was fi.rst observed in the river near Sherman.The ice accumu,lated in masses 3-4 inches thick over 50%of the cobble bed in the near-shore area. Anchor ice was still present in water depths of 4 feet up to 30 feet from shore in the main channel.On contact,the ice masses broke into small platy pieces,very unlike the frazil IIdiscoids ll found flowing at or near the surface.It should also be noted here that during a check of water temperatures near shore,the velocity along the bottom was zero or very close to zero,but 6 inches off the bed water velocity picked up noticeably.The water temperatures near shore in 2 feet of water were uniform throughout at 32°F.Ice on the river bed may have been initiated by ice floes scraping over the bed leaving frazil particles adhering to the cobbles or turbu- lance put frazil particules into suspension allowing them to contact the supercooled cobbles. At the same time anchor ice was observed in the river be- tween Talkeetna and Portage Creek,ice bridges were ob- served through Devil Canyon and upstream to Devil Creek. Plates 5-7 show the locations for these ice bridges as of October 31 -November 1 st. By mid-November,anchor ice could be clearly seen along the length of the river from Talkeetna to Portage Creek.In the main channel,ice appeared to be concentrated in the deeper parts of the channel,but shallow,high velocity areas also had anchor ice formed over 50-70%of the bed.Spring-fed side channels showed no signs of anchor ice formation. The ice bridges between Devil Canyon and Dev:il Creek were sti II in place and several new bridges had formed near Tsusena and Watana Creeks.The most significant new bridge developed just above Watana Creek confluence.The ice cover formation progressed approximately 6 miles upstream by November 13th.Frazil was accumulating at the upstream edge of the ice cover,not being carried under the ice.There- fore,the Froude number at the upstream edge was assumed to be less than 0.08. No ice bridges existed below Portage Creek by mid-November but through constricted reaches slush floes were compressed and completely covered the river surface.Apparent lack of cohesion in the ice prevented formation of ice bridges.The most noticeable channel constrictions occurred just upstream of Curry between cross-sections 24 &25,at cross-section 29, at the bedrock outcrop below cross-section 31,just upstream of Sherman and at the rock point near LRX-43. 4-3 , s5/s On November 11th,at the channel constriction below the Gold Creek bridge (near LRX-43),frazil ice was observed being carried underneath the shore ice and reappearing downstream.Moving ice floes covered appro,ximately 60%of the open channel upstream of the bridge,with average thickness of 0.5 foot.Under these conditions the Froude number was assumed to be greater than 0.12. Plates 1-4 give more description of river ice conditions for the river between Talkeetna and Portage Creek during October and the first part of November.Ai r temperature and precipitation data corresponding to this time period are in- cluded in Attachments A &B. During reconnaissance of the river downstream from Tal keetna on November 13th,periodic bridging and open water were observed.This discontinuous ice cover development was most obvious in the more braided reaches,such as th,rough the Delta Islands.At single channel reaches in the lower river frazil slush accumulated to 100%coverage,but the slush blanket did not consolidate and form ice bridges.Most of the tributaries below Tal keetna had formed ice covers near the confluence by mid-November. The next detailed reconnaissance of ice conditions on the Susitna River was carried out on November 29th.Plates 8-14 document observations made as the ice cover formation pro- gressed upstream from November 29th through December. In the lower river,the leading edge of the ice cover was observed approximately 8.4 miles below the Parks Highway Bridge at river mile 75.5.Upstream from the bridge to Ta'lkeetna,flow was confined to a the main channel which meandered between the east and west sides of the floodplain. Other channels were either ice covered or dry. At Talkeetna an ice bridge was observed across the main channel (see Plate 8)on November 29:No signs of staging were evident upstream of the ice bridge because the far west channel prOVided flow and frazil ice relief. Frazil ice coverage in the Talkeetna River was 40-50%,with most flow through the north channel.There was no sign of an ice cover forming in the Chulitna River near Talkeetna, with approximately 40%frazil ice coverage.The Susitna River at the confluence with the Chulitna showed 80-90%coverage of frazil slush ice,but the channel was still open. On December 1,an ice bridge was observed across the -Susitna River at the Susitna-Chulitna confluence,but the Chulitna River was still open.Evidence of a rise in water 4-4 s5/s leve1 of 3 to 4 feet occurred between November 29 and the morning of December 1 upstream of the ice bridge. On December 3,ground and aerial inspection suggested that the following process occurred at the confluence.The ice cover prog,ressed upstream in the main channel to where the Chulitna and Susitna waters meet.For the ice cove,r to enter the Susitna,thickening of the blan ket raised the water level unti I hydraulics allowed upstream progression.After the cover stabilized in the Susitna,some unknown mechanism failed the cover leaving a relatively neat straight line where the Chulitna and Susitna waters meet,and the Chulitna carried the ice downstream.Following the failure,a drop in water level deposited ice floes on gravel bars and Iban ks downstream from the conf,/'uence and the western channel remained open.At LRX-3,a 3-foot drop in water level was field measured,with a maximum freezeup water elevation of 345.4 feet.Considerable frazil pancake ice and shore ice were pushed up and deposited on the bank.Upstream from this point,the ice cover progressed by a process of juxtaposition. On December 1 st,no other ice bridges closed the channel between the leading edge of the ice cover at river mile 104.3 and Portage Creek.At several channel constrictions,the frazil blanket covered 100%of the river,but floes were not stationary. Over the next two weeks the progression of the ice cover between the confluences and Gold Creek was monitored to determine the rate of ice cover growth upstream.Figure 4.1 gives a graphical picture of ice cover advance during early December.Table 4.3 lists dates,times and observed loca- tions of the leading edge of the ice cover used to create Figure 4.1.The average rate of ice cover growth was 2.7 miles per day.Overall,there was little observed variation from this rate.It is important to note here that during ice cover formation climate data from Tal keetna showed air tem- peratures to be far below normal which would tend to accel- erate the rate of ice cover growth.Streamflow records from Gold Creek are not available for this same time frame.How- ever,average monthly flow for November and January listed in Appendix B,were above normal. December 2,1980 -On December 2 and 3,field observations and measurements were made at the ice cover leading edge near Chase.Figure 4.2 is a plot of water surface profiles at Chase during ice cover formation and Table 4.4 tabulates the field measurements. 4-5 s5/s On December 2nd,the leading edge of the ice cover was below LRX-12.Downstream from the leading edge there were a few open leads where water was flowing over ice frozen fast to the bed.It appeared that the shore ice had been lifted up as the water level rose during ice cover formation and was repositioned and deposited as the water level decreased. Average ice thickness in the center of the channel was esti- mated to be 2 or 3 feet consisting of a slush blan ket matrix filled with water and solid ice. Upstream from the leading edge,the water level was obvious- ly rising and velocity of the oncoming frazil ice floes slowed to zero as new ice was added to the leading edge near LRX-12. At LRX-13,width of open water was 100 to 125 feet and the edge of shore ice was approximately 80 feet from the toe of the right bank.The shore ice was heavily buttered in this constricted reach.Elevation difference from the top of but- tered ice to the water surface was up to 1.5 feet.Depth of water at the edge of shore ice was 5.4 feet.The open water channel was filled with nearly 100%coverage of frazil ice moving at a velocity of approximately 2 feet per second.The thickness of the frazil ice blanket varied,but was approx- imately one foot thick near the shore where it was being compressed and thickened.Observing open voids away from the edge,the frazi I blan ket appeared to have an average thickness of 6 inches. December 3,1980 -The following day water surface elevations were again taken at LRX-12 and 13 after the ice cover had solidified through this reach.Table 4.4 shows that the water level rose 3.3 feet in approximately 24 hours at LRX-13 as the ice cover formed,with no signs of dramatic staging or "disruption of shore ice. The new leading edge at 10:30 a.m.on December 3rd was at LRX-17,the upstream tip of the island at approximately river mile 112.7.Upstream,ice movement was only \to \foot per second.As ice floes were being added to the leading edge, they exerted sufficient force on the slush blan ket to form pressure ridges which thickened the blanket.Though vari- able,an average of 4 to 6 inches of slush ice showed above the water surface. Downstream 100 feet from the LRX-17 there was no movement in the frazil slush blanket.A little further downstream,in the area of LRX-16,the ice was also stationary.Here the slush blanket was buoyed up so that 4 to 6 inches of ice showed above the water surface.Along shore,ice had been lifted up and pushed down the shoreline,forming pressure ridges. 4-6 55/5 By 11 :00 am,the leading edge had advanced to river mile 112.9 just below LRX·18.At this cross section,ice was moving at less than 1a foot per second,wedging itself into the channel,compressing and thickening the slush blanket.The water level was rising noticeably at this time.As staging occurred,water began spilling into the right (west)channel downstream at the island,which had previously been dry. Frazil ice being carried under the ice cover also began flow- ing into the right channel as the water level in this channel rose.Floes accumulated downstream where the split channels rejoined.Ice cover at the downstream end of the island in the main channel had thickened so that new ice floes were not carried underneath the existing ice cover.Instead,an ice cover in the right channel gradually thickened and extended upstream around the island until it formed a continuous ice cover through the 'reach of divided flow below Cross-section 18.This seemed to be the normal process for ice cover formation through divided flow reaches.The ice' cover formed in the main channel blocking the entrance and exit to side channels.As the water level rose during ice cover devlopment,water and frazil ice began flowing into the previously dry side channels.Upstream growth of the ice cover in the main channel was slowed until frazil ice floes accumulated and thickened into an ice cover through the side channel.Once an ice cover had formed and thickened in all the major channels,frazil ice floes began accumulating at the leading edge of the ice c:over instead of being carried under- neath and the ice cover growth began again upstream through the main channel. Continuing upstream from the leading edge of the ice cover there appeared to be little change in the ice conditions along the river th rough Devil Canyon.However,from Tsusena Creek upstream,the channel was severely constricted by shore and anchor ice growth.At Watana Creek,an ice cover had formed which extended upstream to approximately 3 miles above the Kosina Creek confluence by the afternoon of December 3rd.At a few sites there was water spilling into side channels,indicating a rise in water level.However,the exact change in water level during ice cover formation through this reach was unknown. On the morning of December 3rd,a continuous ice cover had advanced in the lower river as far as river mile 86,just above the Parks Highway Bridge.There was no evidence of unusual staging as the ice cover advanced through this reach.However,the water level had risen enough to flood some of the shallow gravel bars,especially on the north side of the bridge.In open leads downstream of the leading edge no frazil was emerging.Upstream of the leading edg'e,an ice bridge was forming through a reach severely constricted by 4-7 s5/s shore ice.Plate 8 shows the location of the leading edge of the ice cover and the position of the new ice bridge up- stream. From the ice bridge upstream to Tal keetna,a single open channel meandered between the east and west sides of the floodplain.This reach of the river remained relatively un- changed over the next few days.Shallow,high-velocity areas caused larger floes to be broken up and hindered formation of an ice cover on the river. December 4 &5,1980 In the river above the Chulitna- Susitna confl uence,the ice cover continued to grow upstream at a rate of approximately 2.7 miles per day.The leading edge of ice was observed at river mile 115.9 on the morning of December 4th and at river mile 118.8 the foll,?wing day. No water surface measurements were taken,but it appeared the water level had risen during ice cover formation.Pooled water was observed on top of the ice below the leading edge. At several sites upstream,frazil slush floes covered 100%of the open channel.These sites were generally locations where natural constrictions such as bedrock outcrops or extensive shore ice hindered flow and caused ice floes to accumulate. Plate 10 shows locations of potential ice bridges due to chan- nel constriction and frazi I ice accumulation,as observed on December 4th and 5th.All of these places had the potential to bridge over under proper conditions,but no bridges formed as the ice cover progressed upstream from Tal keetna to Portage Creek. Upstream of Portage Creek,two small ice bridges had formed between the upstream edge of an older,larger ice bridge and Devil Creek.Other than these new bridges,there appeared to be little change in ice conditions for the upper river. December 8,1980 The next reconnaissance trip for ice observations was carried out on December 8th.By this time, the ice cover in the river below Talkeetna had progressed as far as river mi Ie 93.5.Above this,there was still a single open channel flowing to the Chulitna River. I n the middle river,above the Susitna-Chulitna confluence, the leading edge of the ice cover was observed at river mile 126.35.Downstream of the leading edge,at LRX-29 where the channel was constricted,frazil slush filled the channel.Shear lines or buttering were strongly developed along the left ban k at the contact between shore ice and frazil slush.At the time of the survey,the water level was obviously rising through the reach.Water was beginning to spill into side channels farther downstream.Also,after the 4-8 s5/s initial water surface measurement was taken at LRX-29,ice along shore began shifting,being buoyed up by the rising water level.The drag force from flowing water and ice pressure initiated movement of ice floes in the channel. Movement continued for ten minutes,with ice floe velocities of approximately 2 feet per second.After movement stopped, the water level was slightly lower than it had been prior to movement at the cross section.However,the side channels farther downstream appeared to be flowing more strongly than prior to ice movement.Also,at LRX-28,water was flowing over 20-30%of the ice surface in the channel. When a final check at 12:45 pm was made of the water sur- face elevation at LRX-29,the water level had risen eight-tenths of a foot from the initial reading at 10:00 am and appeared to still be rising. Field measurements of water surface elevations made on December 8th upstream and downstream of the leading edge were plotted with the water surface profi Ie measured in early November to show the effects of ice cover formation on water levels through that reach.Figure 4.3 and Table 4.5 sum- marize the measurements which were made. December 12,1980 -The final reconnajssance trip for freeze- up observations was conducted on December 12th.The ice cover extended as far upstream as Gold Creek.Within three hours,from 11 :00 a.m.to 2:00 p.m.,the ice cover advanced from river mile 136.4 to 136.9,with no sign of dramatic change in water level upstream or downstream of the bridge. As ice floes neared the leading edge of the ice cover thei I'" velocity visibly decreased.At 11 :45 a.m.,the surface veloc- ity of the frazil slush in the channel at the bridge appeared to be zero.Water levels were slowly rising at this site. Farther upstream,at cross-section 47,velocity of ice floes were measured at 2.8 feet per second.Velocities at LRX-48 were 4.3 feet per second. Over a two-hour period,the water level at cross-section 45 rose 0.8 foot.However,ice along shore was broken and tilted at sharp ang les,indicating a greater rise in water level sometime prior to ice cover advance through this reach. Estimated maximum water surface elevations associated with the breakup of shore ice at LRX-45 and LRX-44 were 687.01 and 684.20 feet (MSL)respectively.These can be compared with water surface profiles shown in Figure 4.4 to give max- imum apparent change in water levels in the vicinity of Gold Creek during ice cover formation. 4-9 Upstream of Gold Creek,there were no ice bridges in the channel until just below Portage Creek where a small bridge had formed on the upstream side of a constricted bend in the channel. On December 15th,the ice cover extended upstream past Portage Creek and into Devil Canyon.On December 30th, the ice cover extended intermittantly through Devil Canyon upstream to 4 miles above Devil Creek.Open water persisted in several turbulent flow reaches.Fu rther upstream there was a continuous ice cover with several open leads.Plate 12 shows the approximate extent of ice bridges and open water leads through this reach.Plates 15-18 show the location of open leads that persisted through the winter after formation of the ice cover.Most of these are velocity leads in the main channel thalweg. 4.2 -Breakup (a)Review of Available Historical Records The best information on the nature and timing of breakup of the ice cover on the Susitna River was obtained through the National Weather Service River Forecast Center and the Alaska Railroad. Data from the Alaska Railroad The table below lists breakup dates on the Susitna River from 1975 to 1980 based on observations by personnel from the Alaska Railroad.It also describes the nature of breakup and identifies specific problem sites. Year 1975 1976 s5/s Dates May 12-15 May 5-17 Description I ce out by the 15th.Some minor flooding, no damage to track. Washouts on the 5th on tracks in the vicinity of Curry from river miles 119.8 to 122.Washouts related to large jam extend- ing from river mile 118.4 to 123 during the same time.Short stretch of track also lost downstream of LRX-30 at river miles 127.0 to 127.2.Heavy flooding of tracks in vicin- ity of LRX-18 and just upstream.Signifi- cant ban k scou ring and ice pushed up on tracks from LRX-13 (R.M.110.4)to LRX-18 ( R.M.11 3.0).Ice out on the 17th. 4-10 (Continued) Year 1977 1978 1979 1980 Dates May 16th May 8-9 May 8 May 12-13 Pescription Ice out,some bank scouring,but no signif- icant damage. Some jams and flooding,minor damage.Ice on tracks at curve approximately river mile 109.6,below LRX-13. Gentle breakup,no flooding or damage to tracks. No flooding,ice and rocks pushed up on tracks at a few spots,no serious damage. s5/s Overall,the Railroad has never had ice problems with the track from Sherman upstream to Gold Creek.The t,rack is farther from the main channel of the Susitna and is higher above the river through that reach.However,flooding and damage to the tracks occur consistently in some reaches below Sherman.The track in the vicinity of LRX-30,where the river channel bends to the west,has been damaged often. Rock rip-rap has been dumped to retard active bank erosion during breakup along the far left bank. Another section that appears vulnerable during breakup is that area below Curry from LRX-23 to below LRX-21.Ice jams of varying magnitude form through this reach nearly every year,causing flooding of the tracks or other damage. Farther downstream,active bank erosion is threatening the "tracks in the vicinity of LRX-20.Rip-rap has been dumped to prevent further erosion. Rip-rap has also been dumped through the enti re reach from LRX-18 to below LRX-13 along the left bank.This reach suffers nearly every year from flooding,ice on the tracks and scouring of the banks. The sharp bend in the river channel between LRX 9 and 10 has also been the site of ice jams several times in the past. Water flooded the tracks and ice was pushed up on top of the ban ks,with some scouring occurring. 4-11 Data from National Weather Services (NWS)Records Records from NWS observers are included in the following pages,showing breakup dates for the Susitna River at Talkeetna and Curry,and the Talkeetna River at Talkeetna. The records are not continuous,but help document the pat- tern of ice cover decay and breakup over the past twenty years. The average dates Iisted on the Table 4.6 are based on an assumed key date of February 28.This date is used as a zero point.For each category on the table the difference in days between the key date and the observed date is added to the record total and divided by the number of years of rec- ord to figure the average date.For example,on Table 4.6, the date of last ice on the Susitna River at Tal keetna in 1971-72 was observed to be May 27th.This means last ice was observed·88 days past the key date of February 28th. To figure the average date,88 days must be added to the running total which was 1,427 days in 1970-71.This gives a new total of 1,515 days up to and including 1971-72 which can be divided by the period of record (22 years)giving an average date 69 days past the key date of February 28,or an average date for last ice of May 8. Based on these National Weather Service records,last ice in the Susitna River at Talkeetna for 1980/1981 matched the average date of May 8th. (b)1981 Breakup The breakup process on any river begins in the spring as solar radiation and increasing ai r temperatu res begin to melt the snowpack and cause river discharge to increase. The rising water level puts pressure on the ice,causing fractures to develop in the ice cover.I n addition 1 the solar radiation reduces the insulating snow cover on the ice and thermally degrades crystal bonds in the ice sheet (candl ing). Gradual reduction of the Susitna Basin began earlier due to warmer than normal cloud free days. low elevation snowpack in the than usual in the spring of 1981 early spring air temperatures and s5/s Breakup on the Susitna was predicted by the NWS to be one to two weeks early,based on these early climatic conditions. There was no significant precipitation during early spring to increase runoff in the watershed.Therefore,river discharge did not increase sufficiently to create strong forces on the ice 4-12 cover and initiate breakup.Instead,the ice began to slowly disintegrate in place with long open leads developing through the length of the river. A return to normal temperatures by April slowed the breakup processes occurring in the Susitna Basi:n,and predictions of timing for breakup returned to near normal.Also,breakup was expected to be very mild due to the minimal to non-existent snowpack left in the basin by the end of April and the deteriorating condition of the river ice. Pre-breakup conditions observed duri,ng a reconnaissance trip on April 23rd are referenced on Plates 15 through 22.At that time,open leads were growing by ice calving off the lead perimeter.Ice floes would accumulate at the downstream end. No floes were observed being carried underneath the ice cover.There was also little evidence of rising water level increasing pressure on the ice cover. By May 1 st there were clear signs that the ice cove,r had undergone first movement.Ice accumulations were developing in several locations. For the next few days changes in the chal"acter of ice accu- mulations ~nd water I~vels along the river were monitored, especially at Gold Creek.Increased overflow on top of the ice and fracturing of the ice cover indicated that the water level was steadily rising during the first week of May.Open leads continued to grow and connect. By May 3,the rise in water level and ice movement created ice jams upstream of the Parks Highway Bridge,above Curry where the channel bends sharply and begins to constrict,at LRX -29,above Sherman,downstream from the Gold Creek bridge near LRX-43,above the I ndian River in the vicinity of LRX-51 and LRX-52,and upstream at a constriction in the channel through LRX-56 and LRX-57. Plates 15 through 22 show the locations of these ice jams and trace their development during early May.Table 4.7 shows water surface elevations in the vicinity of these jams during the same period of time. On the morning of May 4th,it was observed that most of the previous days ice jams had released and new jams reformed at several different sites. s5/s The jam through the reach at LRX-56 ano LRX-57 sometime overnight,adding more ice and incre.asing on the ice jam upstream from the I ndian River. bedrock outcrop along the left valley wall at LRX-51 4-13 released pressure A sharp appeared to be the principal factor holding the ice.The far right channel was acting as an overflow channel,conveying flow around the ice and relieving pressure on the jam.Flow in this channel increased noticeably with the addition of ice from upstream.It also appeared that the cehter of the ice jam had sagged due to a change in water level.Parallel shear Jines could be traced through the ice jam along the boundaries of the main channel on May 4th.This apparent drop in water level may have been related to increased flow spilling into the far right channel or the release of the ice jam below Gold Creek. Attachment B shows the USGS streamflow chart from Gold Creek during early May.Timing and maximum water surface elevations resulting from the jam which keyed at the rock point near LRX-43 can be easily read from the chart.On the morning of May 4th remnant ice was stacked up to 6 feet high along both shores upstream and downstream of the bridge. Average thickness of the ice chunks was three feet,but much of it was candled and easily broken apart. From Gold Creek downstream,the main channel was free of ice accumulations until just below Sherman.Sometime during the night of May 3,the ice jam above Sherman released.Ice from that jam combined with upstream ice packed into the main channel through the reach just below Sherman.The ice jam key was located above a reach of shallow,turbulent flow near LRX-32,where the channel bed was extremely irregular. These features apparently instigated jamming.I n this reach of divided flow,the left channel provided overflow relief, carrying flow around the ice so there was little effect on water levels upstream.This jam held in place until sometime during the night of May 7th,as the channel was clear of ice on the morning of May 8th. The ice jam downstream of morning hours of May 4th. existed at Curry broke up LRX-21 and LRX-22. Curry released during the early The ice sheet that previously and accumulated in the reach at s5/s Over the next few days water levels through the jam were measured along with water velocities and are shown on Table 4.7.Figure 4.5 graphically shows the water surface profiles based on field measurements.Water levels above the key of the jam dropped approximately 7 feet after the ice jam released.Prior to release of the jam,ice floes were forced up along the left bank during jam consolidation.Pressure ridges also developed as the floes continued to be compressed.Strong streamflow through and around the jam in side channels persisted throughout the period the jam was in place.Approaching water velocities did not appear to decrease. 4-14 55/s Another ice jam keyed near L RX -17 and extended upstream to the confluence with Lane Creek.On May 4th,there was a noticeable increase in overflow on the upstream ice indicating a rise in water level.Flow had also spilled into the right channel below LRX-17.The ice jam held until the early morning of May 6th,when the jam released.I ce floes packed into the channel extending from approximately LRX-3 up to river Mile 101.8,above LRX-7.On the morning of May 8th the jam was stilll in place.Examination of streamgaging charts from Sunshine indicate the jam released sometime later on the 8th or early on the 9th causing the peak recorded on the Sunshine gage chart. The similarities of the peaks from the two charts at Gold Creek and Sunshine on May 8th and 9th suggest that the last of the ice jams released sometime during this two day period. The large ice jam above the Indian River appears to have released late on May 8th.It is possible that the ice floes were again stopped in the vicinity of the bridge causing the peak on the Gold Creek chart.During the night,water levels dropped as the ice compressed through that reach and/or water began spilling into the overbank area and flow- ing around the lam.Water level s rose again and sufficient forces built IUp to initiate movement of the jam. New ice floes adding to the upstream edge of the jam at the confluence and the flood wave associated with release of the jam at Gold Creek aggravated conditions at the confluence. Water levels were already high through this reach,with water and ice well up into the vegetation on both sides of the floodplain.The accumulating ice floes and rising water level created on unstable situation and the jam released on the morning of May 9th. From the USGS streamflow chart it appears that the same process occurred at the Parks Highway Bridge that was hypothesized for Gold Creek.I ce jammed th rough that reach raising the water level at the gage.Compression of ice floes or increased flow in the overbank temporarily reduced water levels,but late on May 9th water Jevel s had built to a point where the jam became unstable and released. Review of Attachment C,a summary of breakup observations on the Lower Susitna River,shows that water levels peaked in the early morning hours of May 10th,presumably associated with release of the ice jam upstream at the bridge. I ce cover in the lower river had broken up and been washed out several days before the ice moved down from above Tal keetna.Fi rst movement of the ice cover on the Desh ka River and the lower Susitna River at the confluence was 4-15 s5/s reported on the morning of May 2nd.Sporadic movement continued throughout the day in this area.By early evening ice movement was also reported downstream at Susitna Station. For the next few days observers reported continued ice movement in the Susitna,rising water levels and breakup of the ice cover.On May 3rd,the Deshka was 95%ice-free,but a jam had developed at the confluence with the Susitna.The Yentna River was also ice-free except for a jam at the con- fluence with the Susitna River. By mid-day on May 5th,the river at Susitna Station was reported free of ice and the jams at the Deshka-Susitna and Yentna-Susitna confluences had released. Through the length of the river channel,remnant ice was stranded on shore or packed into side channels with little or no flow.Over the following weeks rising water levels flushed out the rest of the ice or it melted in place. Overall,breakup during 1981 on the Susitna River was mild. Ice scarring of trees from the release of ice jams was noticed in a few locations,most dramatically in the vicinity of LRX-7, on the vegetated islands in the channel.However,no major changes in channel configuration or significant scouring of river banks due to ice were observed during the breakup process. 4-16 TABLE 4.1 OCCURRENCE OF ICE AT SELECTED SUSITNA RIVER SITES, DATES PROVIDED BY THE USGS 55/5 Site Denali Vee Canyon Gold Creek Talkeetna Yentna Confluence 4-17 Dates October 1-27 October 22-31 October 15-28 October 7-23 October 20 TABLE 4.2.-. WATE~TEMPE.RATURES DURING'FREEZE-UP (1980 ) :s BELOW SUS/TNA CHULITNA ABOVE TLK. OAT£"·CONF.CON!=".RIVER TIME OESCRIPT!ON 8-8 ,53'.-~LI?X-45 GOLDCR.-RiM wO.TRIP-'"'." 8-/<;1 50~,LRX-45 COLD C/?-USGS WOo TI<'IP~. 9-Z7 43"7-'OOAM LRX.-I-L/BOF £AS'T CNg TLK.MtJTEL 9-2~42'2·30 PM LJeX-4 ALONG LIB OF MAIN Cf/AN. 9-29 40"8:00AM IfJ TLK.SOATLANDING.U/.5 OF R-R..B~/O 9-2"')42°/'35".PM @ TLK.BOAT LANDING',uls of RR.BRIOG 9-30 43°730AM LRX-/ALONe LiB ~MOTEL 9-30 43°IZ:45 PM LRX-/3 ALONG 0/8 10-1 43'j·30PM LRX-44 ALONG LIS 10-3 38-fl:30AM IN SI-I£RMAN CREEK 10-.,3 3~c 11:30AM LRX-3S ALONG LIB 10-4 42~LRX-4 ALONG FAR LEFT BANK 10-7 39°2:00PM LRX-45 GOLD CR.-LJSG5 WQ.TRIP 10-9 39<>10·30 AM LRX-/3 ALONG R/B _10-9 38-4'00 PM LRX-/ALONG LIB 10-:-11 34-"!I;30AM pis OF LRX-16 AT TIP 01="ISt...ANO ALONG Lid OF RT.ch'4NN£L. 10-11 .31 ..2;15 PM tAK.EN'I 'BEL.OW .sURFACE'Iiv'MAlrV 01-. <OP"Sl./S/TNA Jusr ABOVE""Tt..'!<.CONF. IO~/1 34'2·30P-1l7 I/l/ST D/S of TL.K.R'.R.BRIDGe /0-11 34"6:00PM I-RX-I ALONG LIB '-IO-/Z 32·7'OOAM LRX-I ALoNe L/8 10-/2 3/~2:/5"PM LRX-3 -TAKEN I'B£LOWSURh4CG IN MAIN'CJ.iANtVEL ·JUSTABoVt=CONF·.- /0-13 32~7:00AM LRX-I ALONG 1./8 10-13 32#7:30AM TLK.BOAT LANDIN(;,(FIRsr FRAZIL ) /0-/4 .32-2:..30 PM LRX-45 GOLD CR.-AV£"R'A<5£AcROS. CoHANN£L DURING l.",I.Q.SAMPL./N6 *!='IRST FRAZIL IcE IN .sUs/rN~ A80~CI-IUL.CONFLUENCE" OWN.PA. eKD.L.G. DATE.7~/'5·81 #0SCALE..seA L£ ~~~..~~~G~~l;T...~~..r~~A~~E~[TA8LE 11....]::."005Z306 ..DWG.NQ '-:-.f.---1-A----------~ TABLE 4.3 ICE COVER PROGRESSION ON THE SUSITNA 'RIVER ABOVE TAL.KEETNA FIELD OBSERVATiONS Date Time Location of Leading Edge Dec.1 2:30 pm RM 104.3 below LRX-l0 Dec.2 12:30 pm 107.8 below LRX-12 1 :40 pm 108.15 II II II Dec.3 11:00 am 112.9 below LRX-18 Dec.4 10:00 am 115.9 below LRX-19 Dec.5 10:00 am 118.8 below LRX-21 Dec.8 10:00 am 126.35 above LRX-29 1 :00 pm 126.5 II II II Dec.12 11:00 am 136.4 below LRX-45 1 :00 pm 136.8 above LRX-45 2:00 pm 136.9 II II II Average Rate of Ice Cover Formation =2.7 Miles/Day 55/5 4-19 TABLE 4.4 FJELD MEASU R EMENTS OF TH E WATER SURFACE PROFILES ON THE SUSITNA RIVER IN THE VICINITY OF CHASE Water Surface Elevations Cross River October 7 Section Mile Survey Dec.2 (Time)Dec.3 (Time) LRX-9 103.32 378.01 381 .50 (2:05 pm) 10 104.75 391.88 11 106.68 407.66 409.37 (1:35 pm) 12 108.41 421.73 421.47 (1:10pm)423.14 (12:30 pm) 13 110.36 436.41 434.23 (12:45 pm)437.58 (11:55 am) (10/9) 16 112.34 455.13 457.84 (10:50 am) (10/10) 17 112.69 458.41 460.88 (10:30 am) (10/10) 18 113.02 460.67 460.80 (10:15 am) (10/10)462.05 (11:15 am) o o Leading edge on Dec.2 at RM 107.8 at 12:30 pm and at RM 108.15 at 1:40 pm Leading edge on Dec 3 at RM 112.9 at 11:00 am just DIS from LRX-18 s5/5 4-20 TABLE 4.5 FI ELD MEASUREMENT OF WATER SU RFACE PROFI LES ON THE SUSITNA RIVER NEAR LRX-29 Water Surface Elevations Cross River Nov.6 &7 Section Mile Survey Dec.8 (Time) LRX-27 123.3 542.89 546.80 (11:00 am) 28 124.4 553.86 556.99 (10:45 am) 29 126.1 568.37 572.74 (10:00 am)* 30 127.5 578.18 581.97 (11:50 am) 31 128.7 594.06 594.13 (12:15 pm) *By 12:45 pm water level had risen to 573.56 Leading edge of the ice cover was at river mi Ie 126.5 by 1 pm. 55/s 4-21 '~ATION'Talkeetr.a #?t7t W'J , Prior to 1949.data in unsafe for man column was considered as break-up and opening navigation date. TABLE 4.6 BREAK-UP KEY 'DATE ib.1? U.S.DEfARTMENT OF COMMERCE WEATHER BUREAU ALASKA CLIMATOLOGICAL SECTION CENTBR DIVISION NO.5 ¢For coastal stations date sea ice last observed in open water. 01::> I tv tv Season Body of water Unsafe Record fl.vg.Unsafe Record Avg.Date ice Record Avg.Date Record Avg. for Total &Date for Total &Date cnds permit Total 8 Date Last Total &:Date REMARKS Vehicle Years Han Years shipping Years Ice ¢Years ~~(Y'f<;000 d ;'/5-' 19 hO-E-l ,-('c:e Y ,'1 'I 'h 11/---9Q]..-<Is'Su,sitn,,,Ri.ver ./ ::1/y.r- '/;1'/ff2.6 ~J)19'(-t v -17t1 -:27 'I --1//I -- 7~~/0 '>/2-:r ,/4 5/t t..:t:J,,//a~{!~ :9"2 -(,3 I'II i/i,r 2 'If::tj/15"13'-Sh[10713 7l.Jf/'~-r :£'~;'L.J.,11/'/1/1 ,'/I 1~{3,6 ~"2~1J -//2~323 '/'//"---~-/3"//61 1:/7'f I'-t<f'f flY'1!J3 .If tj/ztf1ft</-tJ-0/3/¥/i 8 1//tJ 7"/7'.',,2g~356 I Z"T -':'.07 ""1 g 3561'1.///" 16 ~~19t5,tt -.(,,.,-/~/J/-IV/"7-A'3 --I,I(12 0 ~ NU-t.)":?.R-I'..J ~g 1/'1 356 8 113 I';' (;2'/I(,()'8 J ----,-/Z o~ q *i 1 " 1'1 I Jf/t7-t Y '1/3 ql7 f/3 :,1d '0.3 ---..51/,/!Lf (~S/?,(If /0 ;til Ift~',6 7 ~-,.3/:).~,3.37 <//',:""II-..r J/3,p'~I!IJ 'l/,~7 13fJrc :;J( /1 II , 2 1 file,7i .<-Y-:).0 58 8 "f/Cf or-..."5'0 /0~'-r-l-~/4z.1 5/1 It.q/&lf~t:, ~5j~5i7 %1-~/f7/·'2..-".,'I1~3 '1 11 0 5/7 5eoCf ~/20'1 I~/~ -'' J(Y ~~vt ~~~......N ------ 0$'>~v..'<>-.~~l..,~...........~~. '._.-.i-___..----_._-=--._-- (~ I ~~- ;@.t-~~~.'"()I'-----'---:+C.L¥.:._.- ~.., II I~\ , ~c)l I -_"-1'I -"\ 0"I ...,)\l'-.~d- r I.i)IJo $', -_.-._..-._.._------- I '"~V~I ~ ..I .._-.--.;_.~~---..-..-.--- V~~~~.~ "1p..~~:r ~I I -------_._-_._-- ~cil Q f'\~~"-1'-....---------- 0"I \)-.\('\-C"-. O>d-.~-~<:lV)~~t---- ~$'l'-~\~\"~~:J''~~If1) '"....... cil"1 ~~-..3 ~~~').. @o)I ~e:--::r-\"------~, -II {}.~~:'";)cil ~\?)II) (Y ~~...\1\, ,.~..-_. "'.i: ~$'~.~.~.~\~'v=~~. _...... .-"......-..-.. f \5 .-: :Co , 1 I <9 J ':;i .': ~.,, ~. 1-:.ri ,',,-,: "\'"')-l'\.I "'0>l'--r-.!'-t--"'-,,-."{'I.t:;t !<:r-!'-'":;r'-""I ,,: ., s::oo v j \ 4-23 STATION Curry Prior to 1949.data in unsafe for man column was considered aa break-up and opening navigation date. TABLE 4.6 (cont.)-~'.'(? BREAK-UP KEY DATE 313/• U.S.DEFARTMENT or COMMERCE .mATHER BUREAU ALASKA CLIMATOLOGICAL SECTION CENTER DIVISION NO.5----' ¢For coastal stations date sea ice last observed in open water. ""I tv "" Season Body of water Unsafe Record Avg.Unsafe Record Avg.Date ice Record Avg.Date Record Avg. for Total &Date for Total &Date ends permit Total Date Last Total &Date REMARKS Vehicle Years Man Years shipping Years Ice ¢Years ,••J 3 /0 :J<;ll)O-6J Susitna River "':~II{1/5 117 ---(/1'1 5'!&' 3 t//6"~'0 5/;?f9t1-bl--1j5 1/£ill --t1'1II1/--- 1y-'t-2 -t.3 -'IS 3 '1//5'3 '1/7 -~C;fl()~'I -//5 ---,'I I~I/..,J '1~?>'1/;5 3 '1/1 It>-Y,P/965-"<//,&.,n...-//[.--(,9'1"(/.' ~'itS 3 Y!;5'-3 'i/.r 10 S/:t"/9 N-t)(,I,//~-----6'1.1/ 1r1t>144-nuJ.1f'"rty~t/{3 ~/)//5 3 1/;'/0 5#.f1{,5-r.~.-----61'( 'Jt.~1/.5 3-r;;s ') '1/7 /0 .IqLh-~I -/I!:----'{/tt $13 \ /9fJ7-fJ9 j .,I I./:~.;..-f.•,I;.'/'./"1 -,.--;...'.,....._....'.~ I'L ..-=t=-~R..---, 1--1-I I I,! ---------------_..-. S"-.::iTATION Ta-lkeetnam: TABLE 4.6 (cont.) BREAK-UP KEY DA'l'E"~L~i"DIVISION"NO.5 • Prior to 1949,data in unsafe for man column was considered as break-up and opening navigation date. U.S.DEFARTMENT OF COMMERCE ~mATHER BUREAU l~ASKA CLIMATOLOGICAL SECTION CENTER ¢For coastal stations date sea ice last observed in open water. ~ ~l;;eason Body of water Unsafe Record Avg.Unsafe Record Avg.Dat·e ice Record Avg.Date Record Avg. for Total &Date for Total &Date ends permit Total Date Last '!Total &Date REMARKS Vehicle Years Man Years shipping Years Ice ¢Ye~rs 'I '-I f' ,60-61 Talkeetna River 1t9 '1/1;.:«;tl ~Z/---~'$3 .s-~ ~/-{>y -Ito'!'I 1/1;1 )09 ¥11u -~5"16"I(----533- iw 1I§t S/u.'29("6 i/~<g 1 t./??§jq~Z·t3 ~Jlrv 0--t&-=0.r/,If .:>:.0-..\ c!"~, 'I/;o rh2-b 1/;17 S/36 ,g Silo~3-6Y if "'II;7v7 3'/1 .---71tJ )V<7'7 iii I '1/';'7 f!tf ! 1'- I t/f 1/lJ/ft7~-,I'I I ,,3 3/27<J 3S r Y~o (3---"7Sa ~7g7 ¥/7 7 ~¥I --II ¥/~7r.s:tt,--3?/'7stJ.,., )~~'27'$7 -,kit.!I II fh7,'U-Lt 1 'I 'I ~i/1 -:slv _.-7S0 ~'6 II"]~ifl b ~~jvl II:~a IY 0/'7 I1t1-1,%I (/..-21D -,!--_2:11 J?01 ~i~tiM"1 .;)).-0 III -11>-'1 ii; /3- 5/7 !0,-&7 .,-3/.10 it ]., to 1_£115 10 1'1 5/8 ! '7°-11 ~ _.'V-I 3 (,2 "'-I 52?'1/1-I -.1-/7-9S-~, II I ~/5 II .~/1r'3 ::;., sA I>0/8171-7~."'1/B'~Ol ~ft 591/5;-?1 2.{}9 s-t'7 10 qz I / I .. ._-_.--_._----------------- .t:> I N Ul ....... -~-..--_.--- <:>-~~ ------_.------_.._--,- ~---~~-;To oN ~~ ~N'¢o ':'{t'--~ --.:.~" ~~\" ~.....~ \'"~~~~ \i ,.<'I,I {..\(\i-..~M.r-t--'"'-'"J- ",t--~.t-'""t:<:r-......~i-...., :!-I -(~....~[~ I '1p ~\r,~:::.'~ , ~I _......_~-~--,-...--- ,.".,::r ""I "---------_.___"_R_,__._..~-- (l-.r--~0",)0 V<>....g c;;) ~II,-:r--~t'I)~ ._-- ~''-!'..,<)~~~~~()I' (/"ti \.i):'-. T ...-.'~..-._-~.. f I : ~II -1"( I ;.}<)I l::l (p ; 0-~"< .. W ~o a..'=>I' ~<:; UJ "'"CD .. f5 f-«:, ;- Vl .... Co U '"o.... CJ) ~ 4-26 TABLE'4~7;, ."1JI SUSITNA RIVER BREAKUP OBSERy ATIONS -1981 \.IU:~ W.S.VEL LAl-. WS vEL LI'IX-' wS vEL.. LAX-l. WS.VEL LAX-17 W.S'.V£t. U\X-\I ws.VELW5.VEL" LANE CREEK LAX"11LRIIC-21 WS.VEL..W.6.VEL. COLO \,.RX-12 ) TBM2U ws VEL BElWEEN LRk-a3 , LRll-U lAIC-23lAIC-ULRX-21Sti£RMAH LRX-",OLRX-Je. -~s VE£..t WS vEL ~W...s.VEL.,Ws.V£L_L~ UUt-<l3LAX-44l"'X-46iLA)l-4eLAlC-4S OEVIL CA~YON I PHQ'O••N'L)I ~I~WS"VE~~~~_~3~VEt..~~~~.V£~..J~..!:._~~ ',,'ll' <:\:1.: W4T6'~ TOO H/~JJ C.OULO'" L-AN'D 5eO.34 1(;£ J7""P te.e ~o""IcE ~"o""IC£ 514$4 :~~147t:J40 -14~S.SZ ~t,14'1.97 K't"I"I'-.HJ.I "......~.....1.5615&ICE 511 SO I~C $IJ ",.17 5,r,J.'~ICo! fur3z 4715~J3Z ...15"""~I~/S;5"S"'::~I5"/.J.N .,;~~ SI217 ,,-,e....jS,l140 .9.8 1514....4 ;~ 6S~.6.3 -. t;184J ICE sS'..zz .Zo91 5/ ",.,030 ~,;f,1 - 46"~.,516~0.3 ~tV) ,"6Z It ICE 663 7~ (Z",,"") '6.J~J S.O (7.....,) "32#((""1, 'tf'.CI I~'.'()S"I'5:.6;A4t61"~.l::'M) ---1'---1 I I I I I I ,I I I I I I I 1iB.3.JS 30 ~u.14 (v/f') (Z·~DP,..)&7J09(.ar'6Z?20 4S"1"/B63 ",,4 16 (~':'71."(CV') 90S 80 -16'"J.J - ""Z.~(~£ MAY I ""PAll " M;Y I '074Z ~:l +"8j MAY·- ""AY~,ag,O -• ~ l'l :ol....., .~~!~~~"RIL.0 29jO i£-+-;C :[4 :~ 12l~ •III\.;z:fl M"•64,3'.SII{JO -S'"7Z3S -SU14 ~tJ ISII9&1<£ "uT 37421 -37.i/./3 ...1.3."~D - "1'[", n:'I.,. I.:';:: 10 ':l ~ 71"1'~'i",~~Il-1 I~r MAY,(,44.,-0 NOT~S'"'.S.=""..rrA/$VI/fFAC6 £L£V,qrI<W (,-r.RlJOV6',l'fC,IIN :U;",L£V6'L) VEL.'W"T8A/VElOClry (FT.pelt SCCON¢) S'Lr.~~- ~sr.N.W.•Csr,,,,/ir£b N,fM'w,qr€J/t SU09Fr9CI;;£~£V/fTIOI'I lJ/S ,UPSrR.AH bls 'bOWI'I.srRE,I//I1 ,374,72 -1:373.35 -~4'6P - •J I\) ..... 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PREPARED FOR' FIGURE 4.5 WAr.;~Stl..tF'nCE ..P~O;='IL.t:.s 0 IV r#G .sus /TNJ:1 .f.'IVEA:, /1\1 rHE VICINITY oP c,,~~y L;)U/i'/Nv SP/?//I/(;L3IU::~Kl/P,/98/ ----,------j_. ---~---------r_---------.--------~-----'-~; -=1 :_--~---I ---------------------------:-------'--------------1,",,_._._______--=--=--r-:------! -~-----.-.-----'--------'----.,--------+,---.------·1 .~~--._--.--;----'----------,-Ii --v-'-~:P-:-i::..;..------------~--------~---------'------~· --1---.--.---.----'---------- --I .' --I --I-- ---i ---.--1 --~----- ;------------ ___-=-_J2L.. -,.------~l__.--~~___t_, ,---------------1-- - -+----,---------........----~--;----- -------'------...---.-r--t--~--~-r--.-'---~=_-----~-~=-_-=-=1 ----'----,---'._---+----'----'---_-~~.:_..:._--:_=__=_-_-_-_-=-.r-------1-_-_- t----_.------,,-L--- H--t-~-_;_-_____;c_.'UL ,__lao--==='- -~/f..-x..~/-.--7"'B-r~Hppp-"-·---- ------_._--------- ___.:._ral'1.._---:--- --.- .---2 'IS- -._--~-------- --~-..._------------,,----o ------.--- IQ. -~--_._-- --..::---I{-----I-------- ~----- --~:----+------_.-=-=-:--~---_._-------'-- 11------'----'--- ---:;e -----1 -,-- :....~:--------1--_.t- --&---5-'-i-5'-'1r-----------+-......".~--.:.....--""----------~--------------- ~~-:--~-_. --.-----g['*--------!If--------::---------::.:~~::::==::::::::::::::-----.:--'-I---_-_-==-:........==~_-_-_-. ~-=~-------- ____;_lUVElL21I.L.£:'s -,£..'.~O:S:OS_fJECT./ql'J/-.l.OCI7T1<:MLS -----..----I·._-- ._-..._-_._--------- -----_...__._--~-- -------._-- ----.t1RY _&~- ---~-_.__.-------------- PREPARED R&M CONSULTANTS,INC. 4-32 PREPARED FOR 5 -REFERENCES Bilello,Michael A.1980.A Winter Environmental Data Survey of the Drainage Basin of the Upper Susitna River,Alaska; Special Report 80-19,U.S.Army Corps of Engineers, Hanover,New Hampshire,April 1980. Bishop,Daniel,M.1975.A Hydrologic Reconnaissance of the Susitna below Devi I Canyon i Environaid,Juneau,Alaska I October 1975. Michel,Bernard. Army Corps April 1971. 1971. of Winter Regime of Rivers and Lakes;U.S. Engineers,Hanover I New Hamsphire, R&M Consultants I Inc.1981.Preliminary Channel Geometry, Velocity &Water Level Data for the Susitna River at Devi I Canyon,April 1981. s4/L 5-1 ATTACHMENT A CLIMATOLOGICAL DATA FOR TALKEETNA,ALASKA PROVIDED BY THE NATIONAL WEATHER SERVICE, OCTOBER 1980 -MAY 1981 WITH ANNUAL SUMMARY susiS/s OEG~(E DAYS UEA IWE~TYPH l.S"OV'.n'Q.SKY COv£R TEMPERATURE 'f 8'SE 6s'ON OAtE'S 01=1([PR£CIPlhTIOW S'.u[O~WI NO SUNS~IN£TENTHS OCCtJRAE"IC('"",,LU 11 PRES-r"SlrCjr ,I!:I j:QG """Ul 'SIlOIrII.SUitE '"0 111l( ~~:E;2ltUn r01;-I(;El1H ".c;%~ ,~~~J TIoIUND[ffSTOR"~~:=GAltlJ*l (aUI ~A~ICE ...-~'"z '"~~~~t ICE PEllETS z z .'"I;~~;:"i""~,?~~~~~514UL "[LEI'.~~"~~i!:>u ~~U",~llE.TS 3%u %0""'"-~~"~~~,CLUE 08AH '5 ~Q ~S I~'"-~z z ~~'"~.:>~'"~:zo.,uo.'"'"z .-0-1 DU$JSHIP"",..HEt :;J'"'~~"'"~'"%%00 ~..>~~8=•SI10_[,!CU(,..".5.1..~o.~"0 "I~~~~""00""~%-i 8l01l1lllG SNOW I "'''' I 2 3 4 5 6'7A 78 8 9 10 II 12 13 14 15 16 17 18 19 20 21 n I 58'3e 4a-8 40 17 0 0 0 0 2~.20 01 I .~~.~10 15 ~ I 7 I 2 4~31 J,0 3~2~0 I 0 .24 0 2~.3~112 3 .5 5.~14 I~~7 ? 3 4~30 40 1 35 25 0 0 .01 0 2~OS O~3 .4 ~.5 10 18 ~~J 4 51 30 41 3 34 ?4 0 0 f 0 2'.Ib 02 ~.2 ~.5 12 3~8 8 0 5 01 31 3b -2 35 ?~0 0 .45 0 28 .72 05 I .4 2.'I b 21 10 10 5 6 51 35 43 6 3'22 0 0 .01 0 ?8 67 01 4 .5 5.3 ,31 6 7 46 3b 4\ 1 4 24 0 I a .oe 0 8 19 10 7 8 36 32 34 -?32 31 0 1 T .22 1.7 2~.27 \ 7 5 .0 5.b 13 17 10 10 8,35 2'32 -4 28 J3 0 I a 0 2~.46 35 ~.0 6.J 14 35 8 ~'I 10 34 2'32 -3 29 33 0 I I T 2~.33 ,7 1 .7 4.2 ,IS 10 10 10 II 37 24 31 -4 25 3.0 I T T 2'1.27 01 2 .6 3.0 9 32 ,7 II 12 35 24 30 -4 20 35 0 T a 0 2'.52 01 3 .,'.,,03 8 ,12 13 36 19 27 -7 n 38 0 T a 0 2".4~01 8 .7 '.2 '5 02 13 14 41 32 37 4 28 0 T .24 0 ,.02 10 14 15 44 36 40 7 34 25 0 1 T .23 0'2'.00 .5 ~4 10.8 18 17 'I 7 15 16 40 2~35 3 26 30 a 0 a 0 2'2~03 5.\7.5 \3 03 ~8 I~ 17 41 30 3~•26 2'l 0 0 0 0 28 87102 7.8 8.3 ..05 '0 ~17 18 46 35 41 10 31 24 a 0-T a 29 ~L~01 8.\'1.1 ..3~\0 10 19 I'.7 33 '0 ,JO 25 a 0 .08 a 2'20,02 7.7 8.2 13 03 '0 l'I ~ 20 45 ?,37 7 32 28 0 0 .09 0 2'20 05 2.3 5.2 ~14 20 21 '3 30 37 7 28 0 0 0 0 21 03 ,21 22 &7 36 42 13 27 23 a 0 0 a 2-:'.33;35 ~.2 ~.,13 3~10 9 22 23 45 32 3~"30 ?6 0 a 0 a 2'.07 3~..1 5.8 13 3~1'0 to 23 2'51 3'.,OJ 31 24 0 a 0 o 28."0'3.8 ..,10 OJ 7 7 24 25 46 28 37 , 0 30 28 a 0 0 012'.37 l:4.3 8 13 5 .,25 2~01 23 J2 5 2~33 0 0 a a 2'.38 3.~7 02 5 7 26 27 '45 25 35 ~24 JO a 0 0 o 2'.03 OJ 5.0 5.3 IS 03 8 8 27 2e 34 2b 30 4 35 a I T .07 1.1 b 20 '0 28 2'I 33 28 31 ~30 34 0 I I .03 1.5 2ct.74 35 '.7 2.0 5 02 10 10 2' 30 36 20 28 3 26 37 0 2 T ,2'.L3 01 <11.9 5.2 ,02 0 3 30 31 39 ,.?..a .~..0 2 a a 2'.I I 02 ~.3 8.9 ,.03 0 0 3\ SU"SU"TOTAL rOUl TOT~L TOUl ro~,"£Mt)NTH:r01.llL %SU"SU" \318 a"a"0 ll:Uf'l8E:~OF A"2.J 4 4.3 21 03 roq AVG AVG.AV1i.OEP."YG.1)E"p.P.P~EtIPITAftON DE'-{).HE:21 ~'I~1k.'I'fOHUt "'Hi."Yli. 42,'5 2'.0 35.6 3.7 -121 O.).01 tNeM 12 -0 ..&0 - S!o\$OH TO DATE ~NOW,ICE PELLETS .. NUPAlQER or o.rs TOr"..TorAL ,1 0 INCH 3 CAEA1 Sl [N 24 lolQURS AND OA1(S_CiREUfST O-EPJH ON GI:tOUND or SNON, I"!U{,,1J11 rEI1P ~INt"'Url 1£119 20'5 5 Ht1)NOERS TO~t1S 0 .~IPIUTION _S"IO)l ICE P€:lLPS I CE PELLET c:.OR I CE AND nAT )70 ,32 <3 <0 OEP E.ur rOG 0 .bI 7-a 1.7 a 2 31 • 0 4 0 -114 -I CLriA P.,UU C uor CLOUo.~ o () -1 o OJ rr; ;0 WBAN •?~5?B)45 F'T. MONTHLY SUMMARY ELEVA,TlON I GROUND. Local Cllimatofogical Data LONGI JUD£,50 •O~I WLAlITUOE1)2'Ie 'N OCTOBER I~BO TA~KEETNA,A~ASKA NAT10NA~WEATHER SERVICE OFC TA~KEETNA ArRPORT •'J SUMMARY BY HOURS "[CORO,or wEAIHER TYPES."STE5T OBSERVEO l-I1INUIE WING S'HOS, ,VA.RlQUS.OTHER O~TA M~Y BE INCOMPLETE DUE TO YARUBLE SCHEDuLE PART T THE OPERA TI ON. •Exrl:t£~rCA 'HE ,",ONT ...-LAST OCCuRRENtE IF "OAE tKAN ONt. !TAAC£AHOUNT t ALSO ON AN HRUER 'OAT£.o~DA rES. ",(U1 rOG:-HSIBfllTl If"",ILE O~LESS. rIGUR€S FO~"INO D[~ECTIONS ARE tENS or DE· GAEES ClO(XI.IISE F'tOti TRUE NORTH.00 ,.CAUt. OAf'"IN COLS.SAND 12-1S A~£eASEO ON 7 OR "ORE OBSERurtOll'S PER OAY U 3-l-IOtJR [HTE~l"LS • Fj,STfST "tLE WINO sPEEOS iRE FA.STESf ~BSERVEO ON[-"'INUTE VALU'Eli WHEN DIRtCTlOftlS ARE (~TENS or OE(>REH.T~E ,I.IllH HtE OIRECTION lNOICAT(S PEAle GUST SPEED. ANY ERROR'S DETECTED Will BE CORRECTED ANO C'~ANGES tN SU","ARY OArA.l.Illl BE AHoNOUTED IN TKE ANHUAL SU".,A.RY AY[R4~£S RESUL UHf WINO or •IE HPERA lURE H Qg~>;U~~ z 0 S~:;-.;;:>-~% '"%~:o/-.;::0 '".,~~'"~u ~. I ~~-~z·'".~~o.~:>~gi ~"ox 0.•.z,.0 "Q ~" ,02 9 2'l.22 34 32 2'84 S.02 3., as 9 2'.21 33 3'2'85 5.5 04 2.~ 09 a 2'.21 3J 32 28 83 5.a 04 3.7 II 8 2'.21 J~3~30 7J 7.3 02 4.0..8 2'1.20 4<38 32 70 7.0 36 2.8 17 a 2q.1q 3a 35 JI 79 5.a 02 3.0 20 7 2'.20 35 33 30 82 6.2102 J.3 23 6 ~~.20 35 33 2'82 l).2 1 0'•1 HOURLY 'PRECIPITATION (WATER EOUIVALENT IN INCHES)-NOT RECOROEO ~"~OUR E~IN ".1'P "~aUQ:MO[NG .H. 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(l;.,'J'....,·11 J:V_l'~l ~~Jl.l"n H,)ll't.·.• • I "',~l'l"fI (.II ~tlJ ~(. 1 r r.J(~' lj':;;"'V-l.~•9.lHd Oll r~(ord f')r lhe l~olI)-'9JO p~dod. o:.a of ;'~J Ll,lRO'.i -fht rOH (cunl in {,)h':\of multlplt ()<.o:::...,,.{,tlC~, :'RrV"11 ,!;r,...·I'l(.J O:RfCTICli -R~cord t~rov';h l1ll. .11I.D ():L~C!::::~;•"...·.I.:-r"l~IroJ'C<llf'Cl'M of aC('.(t"('~cl(>ct:l,d~c (q,l"l Uv(""'..:In,",.00 fndici:('\ClI)lIl. I.;~UH :w.=U ',11::0 •s.~o:-C'<1 is h')te~l ~b~~(\otO t-mln:Jl("'f'ollJe wn(·1"j th!'oJI .....cIIQI'l i~'In Cl:t\$()f cc:;n·L·'j. t-:O'n::DlJe co h·ss chon foll cltn('ni't'cllcloH on 8 varillbic 9c~{'dulc.re~nw,lly rC'c('>cd('d l,·lct'llC'nts Arc (["('1:'1' brOkr·n.'H'.c;I.I ..'nCl':>in incOm~l('[.c r'"('cords_Didl~'Ccnl·....r:lcur(·c"crCIIl~'~and pr~'d?Lt8tl"n coc.lb (e>r portions of ch~'rl·cord P.ly b<-fur ochre choUn "catL'n~~'r dr.)·.nu,.'p"riod of [e'cord (Ir :,O~1('1'1.'- r,l.:nts S..rO(Vlt'lt.'r lllllo l;('.n"":":lIciv.,y(·.lr!;, for t'/llt'llIJII1"cJ~lY or ob"'l·rv~cll.lrotll d"y rrllJr to 19G.P. .,.rot"tt\l..·1'l'rLnd P)~O-I?5'~And JnlllJllrV 19(>(1.tn dial,' ""lIt'n l1YIIII/,bl~'.• '"for'thl"I'>l·r{od lY!.1-19::'~Iln~January 19(,8 to dllcc. Ht:c:n(d t1)(,,~wlpl (ICC due.-[(.)h'~s thlln (o~I [Lme "pc.·r'l.lt1"ll ul S t~(:loll. ......~>-.... -.l)~() --..I (),.>"r f t.'-l 'b ~.....f'\ p ~~,L~I: ~~?'\'"'1,"'l')f;"?0'i'O"".;.l'i ~ ~t t .......,"(y~~;t:t I ATTACHMENT B STREAMFLOW RECORDS FROM THE USGS Average Monthly Streamflow for the Susitna River at Gold Creek based on USGS measurements: September 13280 (cfs) October 9057 November 2980 December January 2000 February 2200 March 1680 No streamflow data is available for the month of December,1980. Streamflow records are based on periodic discharge measurements taken at Gold Creek during the winter months: Dates of measurement 1980 October 7 (USGS) October 14 (R&M) November (U SGS) Measured Discharge 9057 7290 2980 From USGS historical streamflow records,the average monthly flow over the period of record (1949 -Present)is as follows: September 11900 (cfs) s5/v October 5600 November 2500 December 1700 B-1 January 1450 February 1200 March 1400 RAting labl~for ._.._S(/!?r."?!/?8..Jf;~t(c::;:::.._a.l:__.b/.QIC;/_t!...r_/l.!a_SJ:iL .._ _..__Besin - - - - - - - -a I:'l'L WOo O.Ha. (rom...r:__.lr/9.4].IO _.. .._.__.__._.__,·from._..._...._.......__/o ...-..-....._......_.....__I.f1'01l1_.._.__._.....~..._/0 •..•..__•••._ •.-..1 -.-'-z=y'-11---"r oF"II .-~r - n rIll J (Ii \I H'"I =-=- ,K".l-(,)j UI ..lltU :lIAltS OLI'AIHMENT OF THE INTERIOR GEOLOGICAL SURVEY (WATEIl RESOURCES DIVISION) Slo.110.L -2 :?2 ?.Q Q Q Tabl.PIa.L Q Thll 13lJl~il appl'(3/J1c {ur c,pen·channel {onJition~.II j~ba~J on /4 JiKharge measurements made dUling _./.?6.7.:-:/2.Z2._._._ ................................_..__..._.__._._.__. •__....._and il ...._._well denned bel,,"cen ..:1,,?~.9.__cr~anJ .G...s:R.Q_Q._..cr~. lX.~..r..?I.:.~.?.!y..'~::i ..r:::;-'?:.~t;(/:-:;.";:e:../;'?C7.-/,.6 !__.[.~c;:o.ccr:..__(/P.C!/y.__'lp~r./q:7:'./1?Z::/.?z?-..-.. '".z./!.:.Q.-'::!/.<Co:~:/.l.j .._./??5/:.__..__...__.__. .'_'_ _..__.__..._____.._.. Compo by :7.~f _date .$:3::?? CkJ.by .•_....._d.lle ._.__••.•. 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'"..'-1 '"~0 ~ , ()t ... ~), ~Q ~~~~ '-l ATTACHMENT C SUMMARY OF BREAKUP OBSERVATIONS ON THE LOWER SUSITNA RIVER AT THE DESHKA-SUSITNA CONFLUENCE SUMMARY OF BREAKUP OBSERVATIONS ON THE LOWER SUSITNA RIVER AT THE DESHKA-SUSITNA CONCLUENCE * Date April 18 April 19 April 20 April 22 Time 3:00 a.m. 3:00 p.m. 3:00 a.m. 7:30 a.m. 3:00 p.m. 2:00 a.m. 7:30 a.m. 12 noon 7:00 p.m. 7:00 a.m. 8:00 p.m. Observations Desh ka River:46 11 from top of ice to river bed,32"ice thickness,lower 2/3 of ice is clear and hard 3 11 from top of ice to water level in auger hole Deshka River:drilled new hole 20 11 east of previous hole,53"from top of ice to river bed,26"ice thickness, warm day,melt water on top of ice, overflow ice getting soft sunny morning,rain clouds and showers in p.m.,raining in Talkeetna Mts.and north Susitna River:drilled hole 85 feet off Deshka-Susitna shelf into Susitna 10.3 1 from top of ice to river bed (rocks),28 11 ice thickness,2.5 11 from top of ice to water surface in auger hole,top 9"of ice opaque and grainey,bottom ice clear and hard (splinters off auger),water clear water and ice in Dashka and Susitna have rise 1",water flowing out of auger holes in Deshka,water 2.5"below top of ice in Susitna auger hole,ice thickness same,ice audibly cracking,water and ice have risen another 1" sunny day water and ice raised 2 11 overnight in both Desh ka and Susltna,water flowing out of auger hole in Desh ka but not Susitna (water still -2"below top of ice) water and ice reached 7"above starting reference point in both-Oeshka and Susitna April 23 1 :00 a.m. 3:00 a.m. 7:00 p.m. s7/a 35° 28°Susitna:water and ice 7"above reference point Deshka:water and ice 9"above reference point Susitna:water and ice 11"above reference point Deshka:water and ice 12"above reference point C-l SUMMARY OF BREAKUP OBSERVATIONS ON THE LOWER SUSITNA RIVER AT THE DESHKA-SUSITNA CONCLUENCE * (CONTINUED) Date April 24 Time 2:30 a.m. 7:00 a.m. Observations sunny f high thin cloudiness Susitna:12"above reference point ice =26 11 thick Desh ka:1411 above reference poi nt ice =25 11 thick Dish ka:21"above reference local ice broke loose from sides Deshka:22"above reference Desh ka:22 11 above reference Susitna:ice has floated up,water not flowing out on top of ice Desh ka:23 11 above reference lower level sand bars flooding April 25 April 26 April 27 April 28 April 29 7:00 a.m. 7:00 p.m. 7:00 a.m. 7:00 p.m. 7:00 a.m. 7:00 p.m. 7:00 a.m. 7:00 p.m. 7:00 a.m. 7:00 p.m. Susitna: Deshka: Susitna: Deshka: Susitna: Deshka: Susitna: Dishka: Deshka: Desh ka: 22"above reference 23"above reference 17"above reference 18"above reference 18 11 above reference 1411 above reference staff dislodged 20 11 above reference 24 11 above reference 24.5"above reference April 30 May 1 May 2 58° a.m. p.m. 7:00 a.m. 5:00 p.m. 9:30 p.m. a.m. 10:40 a.m. s7/a frosted last night daily high temperature Desh ka:25 11 above reference Desh ka:26"above reference more water on ice edges in both Susitna and Deshka raining early Deshka:28 11 above reference Susitna:ice jam u/s at cutbank breaking up,beginning to move downstream Desh ka :35"above reference Deshka:36"above reference point Susitna:ice broke at curve and moved Deshka:ice broke at island,movement stopped,estimated movement =1000',no rise in water level ice pieces grounded on C-2 SUMMARY OF BREAKUP OBSERVATIONS 'ON THE LOWER SUSITNA RIVER AT THE DESHKA-SUSITNA CONCLUENCE * (CONTINUED) fast and powerful move ice moved at first bend,all still solid ice cover u/s from Date May 3 May 4 Time 6:05 p.m. 10:30 a.m. 11 :10 a.m. 12:30 a.m. 2:30 p.m. 3:55 p.m. 2:45-3:45 9:30 p.m. 10:15 p.m. 2:30 a.m. 3:30 a.m. 10:45 a.m. 57/a Observations shallow bar at bend in Susitna Deshka:moved sporadically throughout the afternoon,1:40/2:20/3:00 p.m.Trapper Creek reported movement and jam at 4:00 p.m.,large,thick ice in jam,water level rise of 8-10 ft. ice movement reproted at Susitna Station Deshka: Susitna: open but 1st bend Deshka:95%ice free,intense movement and grinding of ice into smaller pieces (4 to 10 ft.square),then cleared out, water velocity estimated to be 10-12 MPH velocity slowed by early afternoon Susitna:water level rising,channel still jammed dis from confluence of Deshka Deshka:water level 91"below TBM (nail in stump) Susitna:ice released between first bend and slough (Kroto slough) On flight to Susitna Station noticed Yenta River almost ice free except at confluence with Sisitna,in the Susitna noticeable ice movement,ice floes moving in II bunches ll Desh ka:rejammed again,ice tightly packed Deshka and Susitna jam released,ice at second bend in Susitna broke and moved dis (rainy and cool all day) ice jamming and moving in both Deshka and Susitna,water level appears unchanged from previous day (too dark to see well) water level dropped drastically,ice pieces stranded along shore,anchor ice exposed along ban ks where previously under water water level 160 11 below TBM,water level appears to still be dropping,more sand bar exposed off point,(estimated highest water level to be 4 11 above yesterdays reading at 2:30L still have anchor ice along shore, banks stilt frozen cannot put in staff gages yet C-3 SUMMARY OF BREAKUP OBSERVATIONS ON THE LOWER SUSITNA RIVER AT THE DESHKA-SUSITNA CONCLUENCE * (CONTINUED) Date Time Observations May 5 9:00 a.m. 1 :30 p.m. 2:00 p.m. 7:00 p.m. Deshka:water level 155"below TBM Susitna Station reports river free of ice, water level rising,dislodging ice from banks on first bend,ice floes moving throughthis reach of the Susitna all morning form u/s Deshka:water level 149"below TBM Susitna:increased ice floes in Susitna channel May 6 9:30 a.m. 2:00 p.m.- 5:00 p.m. 4:00 p.m. 8:30 p.m. Deshka:water level 150 11 below TBM,water velocity slower Susitna:water velocity appears the same, still flowing ice and debris Susitna:channel fillded bank to bank with flowing ice snad bar off point just underwater Desh ka:water level 127"below TBM Susitna:amount of ice moving in channel has decreased by 9:00 p.m. Dishka:water level 13211 below TBM Deshka:108 11 below TBM Deshka:102"below TBM 106"below TBM Deshka:124"below TBM 115"below TBM water level 138 11 below TBM no ice flowing in channel heavy ice flowing in channel amount of ice flowing decreased Deshka: Susitna: Susitna: Susitna: Deshka:85 11 below TBM -water level peaked and receded Deshka:95 11 below TBM 100 below TBM Desh ka:111 11 below T BM,most shore ice has melted or floated away 8:00 a.m. 1:15 p.m. 3:00 p.m. 4:00 p.m.74° 7:30 p.m. 9:45 a.m. 7:00 p.m. 7:00 a.m. 2:00 a.m. 10:30 a.m. 10:00 p.m. 9:00 a.m. 8:00 p.m. 8:00 a.m. May 11 May 12 May 10 May 9 May 8 May 7 *Summary based on observations and measurements made by Leon Dick s7/a C-4 <t !xl-tr Z >..:-' a:CI)1;;0;:) <t CI)~-I.LJ ~Z <15 l<r > (J)<t :lC :E " ;:):lC I~I.L ."CI)I.Ll U ::: d5 I.LJ 0 Z I ....rz :;3<t I~0~ ~ It: ;:)!:z <t LtJ 0 :!oR z ~I.LJ lLI - " ::E 0 ~ ILl >}~:~0 u ~II ~i=I \n W I-iT ~~I~It:t!) ~~~I \1zI.L 3 '\....,I iL::J /I \a:CI.L L.>I I~-;; ILl II I0r'I~Ij \ I--"V V -i....,........---,./.. V j J [7 l/ ...a/, ,. i t 150 140 130 120 110 100 90 80 *~ (J)70LtJ :t: U ~ 60 ILl U I.L 0 50 Q. 0 I- "'- ~40 ILl> ILl ~ a:30 I.LJ I- <t 3 20 10 0 18 19 20 21 22 23 24 25 26 27 28 29 30 I APRIL 2 3 4 5 6 7 8 ,10 II IZ. MAY ...LEVEL OF WATER OR ICE SURFACE BASED ON ARBITRARY DATUM ESTABLISHED BY LEON DICK OWN.OEP CKD.LG DATE.5-14-91 SCALE.N/A R&M CONSULTANTS.INC. .NOINIiI!AA OIliCU..OOI8T8 PLANNe.a suRVEVORS THE DESHKA -SUSITNA CONFLUENCE BREAKUP REPORT BY LEON,DIC~ C.-6 FB.N/A GRID.N/A PROJ.No.052'303 DWG.No.