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<br />. r <br /> <br />> <br /> <br />SUPPLEMENTAL 100-YEAR FLOOD STUDY <br />SURFACE CREEK, DELTA COUNTY, COLORADO <br />SEPTEMBER 2001 <br /> <br />1.0 PURPOSE OF THE STUDY <br /> <br />This Study was prepared to establish the regulatory I OO-year flood plain for Surface <br />Creek in the unincorporated County, from R75 Road to above U50 Road, The results of <br />this study will enable the County to implement the guidelines of the National Flood <br />Insurance Act for new growth being experienced in this area ofthe County. This study <br />will supplement existing flood study data for Delta County and will extend flood plain <br />mapping into an unmapped area. The need for this study was presented in a "Needs <br />Assessmentfor Floodplain Map Revision", prepared for Delta County, September 1999, <br /> <br />2.0 PAST STUDIES <br /> <br />A Flood Insurance Study was completed for Delta County, Colorado in 1983 (revised <br />1991). The past study included the lower portion of Surface Creek from approximately <br />1.3 miles above the confluence with Tongue Creek to approximately 1,2 miles above City <br />of Orchard City. <br /> <br />3.0 AREA STUDIED <br /> <br />The supplemental study for Surface Creek starts immediately above R75 Road, <br />approximately 10.1 miles above the confluence with Tongue Creek, and approximately <br />1.87 miles above the termination of the detailed study from the 1983 document (revised <br />1991). The supplemental study extends 3.9 miles from R75 Road to a point <br />approximately 4110 feet above U50 Road. The study area is shown on the vicinity map <br />attached. <br /> <br />4.0 BACKGROUND INFORMA nON <br /> <br />Surface Creek has its headwaters in Grand Mesa National Forest on the Grand Mesa <br />Plateau approximately 9 miles northeast ofU 50 Road. There are numerous small <br />reservoirs in upper part of this drainage used for irrigation and municipal water storage. <br />These reservoirs were constructed in the early to mid 1990's, There are also small <br />irrigation diversions from Surface Creek. The Surface Creek drainage, through the study <br />area, is a steep side drainage cutting through the lower mesa of Grand Mesa. The channel <br />slope is approximately 6-percent slope. The creek bed consists of cobbles and boulders <br />and the overbanks are heavily vegetated with trees and shrubs. <br /> <br />1 <br />