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~-~- CHAPTER 5 FLOOD RISK ASSESSMENT SUMMARY OF DEVELOPMENT AND CHALLENGES Fountain Creek and Tributaries Developed urban areas make up 12 percent of the Fountain Creek watershed. The remaining land is primarily grazing (58 percent), forest (25 percent) and agricultural (4 percent) land. Projected growth and associated water demands for the City of Colorado Springs created the need for additional sources of water from outsioe the natural watershed. Projects have been constructed to transport water from the western face of th(: Continental Divide eastward to Colorado Springs. Development and inherent replacement of permeable ground with impermeable asphalt and concrete pavements has increased the volume and speed of runoff into Fountain Creek and its other tributaries. The trilIls-mountain water that enters Fountain Creek after use and treatment by Colorado Springs ha'; generally increased the natural base flow in the creek. Once an intermittent stream with a mea[l annual flow of 50 cubic feet per second (c.f.s.), Fountain Creek has developed into a perennial stream wi1l1 a mean annual flow of greater than 230 c.f.s.. The City of Colorado Springs Water Resources Development Department is planning . to meet the needs of 900,000 residents by the year 2040. This would reflect a near three fold increase over the city's current population. Unoer this projection, the mean annual flow of FOlilltain Creek is anticipated to increase to 600 c.f.s. by year 2040. The result of these on-going changes to the area demographics, land US(:, increased stormwater runoff, and an increased base flow has created instability in the stream system. The highly erodible sediment laden stream attempts to adjust and achieve a new equilibrium through increased sediment transport and bank erosion in some reaches and sediment deposition in other reaches. On average it is estimated that Fountain Creek contributes 250,000 tons of sediment annually to the Arkansas River. The watershed is estimated to be losing up to 700 tons of sediment daily. The sediment itself is the leadiIlg cause of stream water quality degradation. The State of Colorado has listed Fountain Creek as a high priority "Watershed in Need of Restoration" within the second list of Category I Watersheds under the Colorado UnifIed Watershed Assessment (1998). Fountain Creek is also listed as a priority watershed of concern in the Colorado Nonpoint Water Source Managcment Program. These listings are primarily based on severe sediment related water quality problems. The Pikes Peak Area Council of Governments (PPACG) had utilized a grant from the Envirorunental Protection Agency to fund the Fountain Creek Watershed Project from 1995 until September 30, 1998. The project brougbt much needed attention to the problems created by streambank erosion and flooding along Fountain Creek and its tributaries. The project concluded that an integrated and coordinated Post Flood Assessment Report 35 Chapter 5 - Flood Risk Assessment Draft Revised 09/09/99