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CHAPTER 5 <br />FLOOD RISK ASSESSMENT <br />SUMMARY OF DEVELOPMENT AND CHALLENGES <br />Fountain Creek and Tributaries <br />Developed urban areas make up 12 percent of the Fountain Creek watershed. The remaining <br />land is primarily grazing (58 percent), forest (25 percent) and agricultural (4 percent~ land. <br />Projected growth and associated water demands for the City of Colorado Springs created the <br />need for additional sources of water from outside the natural watershed. Projects have been <br />constructed to transport water from the western face of the Continental Divide eastward to <br />Colorado Springs. Development and inherent replacement of permeable ground with <br />impermeable asphalt and concrete pavements has increased the volume and speed of runoff into <br />Fountain Creek and its other tributaries. The trans-mountain water that enters Fountain Creek <br />after use and treatrnent by Colorado Springs has generally increased the natural base flow in the <br />creek. Once an internuttent stream with a mean annual flow of 50 cubic feet per second (c.f.s.), <br />Fountain Creek has developed into a perennial stream with a mean annual flow of greater than <br />230 c.f.s.. The City of Colorado Springs Water Resources Development Department is planning <br />to meet Yhe needs of 900,000 residents by the year 2040. This would reflect a near three fold <br />increase over the city's current population. Under this projection, the mean annual flow of <br />Fountain Creek is anticipated to increase to 600 c.f.s. by year 2040. <br />The result of these on-going changes to the area demographics, land use, increased stormwater <br />runoff, and an increased base flow has created instability in the stream system. The highly <br />erodible sediment Iaden stream attempts to adjust and achieve a new equilibrium through <br />increased sediment transport and bank erosion in some reaches and sediment deposition in other <br />reaches. On average it is estimated that Fountain Creek contributes 250,000 tons of sediment <br />annually to the Arkansas River. The watershed is estimated to be losing up to 700 tons of <br />sediment daily. The sediment itself is the leading cause of stream water quality degradation. <br />The State of Colorado has listed Fountain Creek as a high priority "Watershed in Need of <br />Restoration" within the second list of Category 1 Watersheds under the Colorado Unified <br />Watershed Assessment (1998). Fountain Creek is also listed as a priority watershed of concern <br />in the Colorado Nonpoint Water Source Management Program. These listings are primarily <br />based on severe sediment related water quality problems. The Pikes Peak Area Council of <br />Governments (PPACG) had utilized a grant from the Environmental Protection Agency to fund <br />the Fountain Creek Watershed Project from 1995 until September 30, 1998. The project brought <br />much needed attention to the problems created by streambank erosion and flooding along <br />Fountain Creek and its tributaries. The project concluded that an integrated and coordinated <br />Chapter S - Flood RiskAssessment <br />Post Flood Assessment Report 35 Drajt Revised 09/09/99 <br />