FLOOD01595 - Laserfiche WebLink

Home Browse Search

Table I South Platte River Stream Gage Data in Morgan and Washington Counties, Colorado Ga~!! Location Dralnaqe Area Perfodof Record (square miles) 13,245 October 1952 to present 14,810 1944 through 1958 J6,852 October 1916 toprOS!!flt Weldona fort Morgan Balzac . Tho western boundary of the South Platte River basin is fonmed by the Continental Divide with elevations up to about 14,200 feet and the Laramie Range with elevations up to about 10,000 feet. At the southwestern corner of the basin, the mountain area known as South Park is located. This area Is nearly flat and has an elevation of about 10,000 feet. It is surrounded by mountaIn ranges varying in elevation from 12,000 to 14,000 feet. Tho Tarryall Mountains fonm the northeast boundary of the South Park area. Elevations in the plains regIon vary from approximately 7,000 feet along the footh Ills to approxlm.,te1v 4,070 feot at the Washington-Logan County line. Developmont on the Flood Plain The South Platto River flood plain in Margan and Washington Counties Is utilized prim"rily foragrlculturaJ purposes. Exceptfor the areas adjacent to incorporated communities such as Fort Morgan, existing flood plain development is mostly fanm~tead~ and ranch ",,,1 ''''~~~ n. .~.""~. , Source of Data .!nd RecordS A considerable ~mount of historic stream gage data does exist for the South Platte River Which Is pprt;nent to Morgan and Washing- ton Counties. The U. S. Geological Survey ha~ published Info~tlon collected at the South Platte River stream gages in~rganCounty. 3 Information from these gages was used in the hydrologic analysIs conducted during this study. Information on past floods was obtaIned from Corps of Englneprs flood records. The. photograph base fOr the flooded areas are aerial photograph~ taken during the flood period In May 1973 by the Colorado Water Conservation Soard and the Corps of Engineers. Cross section data utilized In thlsstudyw<ls supplied by the Corps of Engineers. High water mark data from the flood of May 1973 waS coordinated and obtained In part by the Colorodo Water Conservation Board with sup- plementallnfonmatlonbytheCorpsofEnglneers,theU.S.Geologlcal Survey, and the Bureau of Reclamation. U. S. Geological Survey 7.S minute quadrangle maps with 10 foot contour Intervals were also used in the study. , . Flood Season and Flood Characteristics Flooding along the South Platte River in Morgan and Washington Counties normally occurs from May through September with the most frequent flooding occurring during June. Annual peak discharges, however, have been recorded from rebruary through October. Floods in Morgan ~nd Washington Counties normally occur under ~-Ice atfectedoondltlons. Icejams,however,..reposslbleeventhough their historical frequency of occurrence Is rare. Floodwaters on the South Platte RIver in Morgan and Washington Counties can result from Intense localized rainfall or general rains, ~lthAr of whiCh m~y be augmented bv snowmelt. The Intense raInstorm floods result from Intense raInfall over areas of relatlvllly smell areale><tent. These storms can produco<!xtremely rapideoncentra- tlons of floodwaters and ensuant rapid rises In stream !evels. Because of Ilttl€ warning time prior to str~ms attaInIng flood stages, this type of storm can produce floods which are extre~ly hdzardou~. This type of flood produces hIgh peaK dIscharge on trlbu- tarl,,~ In the genpr,,! vicinity of -the rllln5torm. Th" discharge,