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Section 3 Hvdraulic Characteristics for the Studv Stream Reach . Using the flood hydrology described above and detailed topographic mapping (from 1985 aerial photography for the reach between Palisade and Fruita and from 1982 aerial photography for the reach between Glenwood Springs and the east end of DeBeque Canyon), other parties (FEMA and the Corps of Engineers) prepared detailed hydraulic analyses that can be used for all of the 8 ponds except Island Acres Ponds. At Island Acres a local approximate hydraulic analysis had to be conducted since no floodplain study had been performed. tOO-year and 50-year flood depths at each site except Island Acres were computed by comparing flood elevations from the detailed hydraulic analyses cited above to ground elevations at the site, CWCB staff conducted field surveys and inspections of existing ground elevations at each site. At Parachute Pond available topographic mapping was deemed satisfactory for determining ground elevations. At Connected Lakes State Park (2 Connected Lakes and Duke Lake) a partial field survey was conducted because of time constraints. The survey of high ground extended from the upstream end of the park to a point about halfway downstream in the park. No data were collected from there downstream to the west end of the park. High ground elevations are unknown for the west end of the park. For all of the ponds except for Island Acres Ponds the surveys consisted of ground profiles for the "ridge" of high ground between the ponds and the Colorado River (parallel to the direction of flow). For Island Acres Ponds the survey consisted of a cross-section (perpendicular to the direction of flow) through the middle of the State Park. The cross-section started at the opposite side of the river from the park (the south bank of the river) and then extended through the park to high ground near 1-70. From that single cross-section one can only derive an approximate estimate of flood elevations and flood depths at Island Acres State Park. For each pond except the Island Acres Ponds a profile sheet comparing existing ground elevations to 100-year flood elevations is included. In each case a profile of high ground parallel to the Colorado River was field surveyed. Since that "ridge" of high ground is the feature that would provide protection to the pond, it is the feature that needs to be compared to flood elevations. The profile sheets are included in Section 5 (Subsection 5.2) along with a discussion of the flood depths at each site. It is important to remember that the elevation of that ground is not the only characteristic that determines whether flooding would be a problem at a particular site. The width of the "ridge", the steepness of its side slopes, its permeability to water, and its stability in the face of erosive forces must also be considered. Those parameters will also be considered in Section 5. CWCB staff did not find any detailed topographic mapping of the DeBeque Canyon, including Island Acres State Park. No detailed floodplain mapping of the canyon has been prepared. In order to estimate flood conditions at Island Acres, another approach had to be taken. A cross-seotion of the river, including the overbank area where the state park is located, was surveyed. The Cameo stream gage is only a few miles upstream of the park, so the peak flow values at that site could be used for an approximate hydraulic analysis. That analysis provided a preliminary estimate of the depth of flooding at Island Acres (at least at the location of the cross-section) during a 50-year and a 100-year flood. Since the park is about 0.5 mile long, it would be helpful to have more topographic information than a single cross-section to describe the flood risk there. 9