FLOOD08504 - Laserfiche WebLink

Home Browse Search

INTRODUCTION This flood plain management report was prepared by the U.S. Departmen~ of Agriculture, Natural Resources Conservation Service, in cooperation w1th the Colorado Water Conservation Board, EI Paso County, and the Town of Calhan, Colorado. Interpretations of the flood plain management study and recommendations to reduce damages are included; however it is beyond the scope of this report to provide detailed proposals or plans to rectify the flooding problems. Authority for funding flood plain management studies is provided by Section 6 of Public Law 83-566, which authorizes the U.S. Department of Agriculture to cooperate with other federal, state and local agencies to make investigations and surveys of the watersheds and rivers and other waterways as a basis for the development of coordinated programs. In carrying out flood plain management studies, the Natural Resources Conservation Service is being responsive to Executive Order 11988, entitled -Flood Plain Management-, and Executive Order 11990, entitled .protection of Wetlands. (both effective May 24, 1977). DESCRIPTION OF STUDY AREA A. Ob~ectives The objective of this study is to provide detailed flood plain management information and mapping to the El Paso County and Town of Calhan for use in implementing flood plain management programs which will minimize potential flood damages. Included in the report are engineering and. hydrologic data which will facilitate the development of a flood pla1n. management plan, road and bridge designs, and flood control measures (1f needed) . . . A. B.sin ~~racteristic8 The watersheds that produce runoff in Calhan are relatively small in size (total area: 3.0 sq. miles). Elevations range from 6950 ft at che upper reaches of the watersheds to 6500 ft at the nQrthern boundary of the Town of Calhan. Slopes range from 4 percenc to 0 percent. The soils in the basin, along the stream channels, are of hydrologic groups B and C. They are moderately deep to deep, well drained soil formed in mixed alluvium and wind-laid materials derived from arkosic and calcareous sedimentary rocks. The vegetation in the watersheds is predominantly native range in fair to poor condition. There is approximately one quarter of the lower basin which is occupied by residential and commercial properties. Most of these properties are located in the northeast corner of the lower basin. The flood plains, within the study limits, generally contain typical residential and commercial property improvements such as buildings, yards, fences, streets, vehicles, etc. Vegetation such as lawns, shrubs, trees, flowers, and forbes are a part of the landscape. There are some willows and cottonwoods along those channels that have a sustained water supply. The channel does a considerable amount of meandering which enhances the visual aesthetics and wildlife habitat values in the area. The mean annual precipitation for the basin ranges from 16 to 20 inches. There is no precipitation record for the Town of Calhan. A climate station in Eastonville. a town which is 15 miles due west of Calhan, has a mean annual precipitation of 17.36 inches with July and August accounting for the greatest monthly values (2.78 in. each month), Snowfall does occur throughout the winter period however there is no large accumulation. An analysis into the contribution of spring snowmelt ,. to flooding suggests it is not a significant factor. Late Spring and Summer rains are the most likely to produce flooding in the scudy area. B. Authoritv . Section 37-60-106(~J (c), Colorado Revised Statutes, author1ZeS the Colorado Water Conservation Board 8to designate and approve storm or floodwater runoff channels or basins, and to make such designations available to legislative bodies of cities and incorporated towns, to county planning commissions, and to boards of adjustment of cities, incorporated tOWD3, and counties of this state8. The board provides assistance to local governments in development and adoption of effective floodplain ordinances. In addition, the board will provide technical assistance to local entities during the performance of flOodplain informacion studies within Colorado. Presently, direct financial assistance for the performance of floodplain studies is no longer available from the board. S~ction 3Q-28-111 C.R.S. for cou.~ty gove~ments and Section 1-23-301 C.R.S. for municipal governm~~ts of the Colorado Revised Statutes state the cities, incorporated towns, and counties within the study. area may provide zoning regulations .... To establish, regulate, restr1ct, and limit such uses on or along any storm or floodwater runoff channel or basin that has been designated and approved by the Colorado Water Conservation Board, in order to lessen or avoid the hazards to persons and damage to property resulting from the accumulation of storm or floodwaters ..." Therefore, upon official approval of this report by the Colorado Water Conservation Board, the areas described as being inundated by the 100- year flood can be designated as flood hazard areas and their use regulated accordingly by the local governments. Flood plain management studies are carried out by the Natural Resources Conservation Service as an outgrowth of the Fecommendations in A Reoort bv the Task Force on Federal Flood Control PoliCY, House Document No. 465 (89th Congress. August 10, 1966), especially Recommendation 9(c), Reoulation of Land Use, which recommended the preparation of preliminary reports for guidance in those areas where assist~~ce is needed before a full flood plain information report can be prepared or where a full report is not scheduled. c . , . , . , . <