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<br />DRAFT <br />SOUTH BOULDER CREEK HYDROLOGY - TECHNICAL ASSESSMENT AND SCOPING <br />December 15, 200 I <br /> <br />A. Critical Component Analyses for a Complete Hydrology Study <br /> <br />· Recompilation and Evaluation of Historical and Gauged Data Reliability <br />· High Resolution DEM Data and GIS Capabilities <br />. Statistical. Analysis <br />. Synthetic Rainfall-Runoff Analysis <br />· Obtaining Paleoflood Data and Integration in Above Analyses <br /> <br />B. Critical Elements to Include in a Complete Hydrology Study <br /> <br />DATA AND RESOURCE NEEDS <br /> <br />· Eldorado Springs Gage Analysis - Detailed gage records over 100-years offers a lengthy <br />history to validate annual and peak runoff for calibration purposes. Details of the 1938 and <br />later flood events may offer insight to the affects of Gross reservoir and other inadvertent <br />storage along with a balanced review of rainfall and snow melt with respect to observed <br />runoff. Any rainfall-runoff model must be calibrated and verified against the observed flows <br />at this gage. <br /> <br />· Adequate Topography - Current local topography for in-city and close proximity county <br />areas is based on the 1993 mapping by Merrick. High-resolution digital elevation mapping <br />(DEM) topography for the area is necessary for hydraulic analyses and flood-inundation <br />mapping. DEM may also be used for the upper basin for hydrologic modeling needs. The <br />DEM is available for most of the Colorado Front Range through the U.S. Geological Survey <br />as well as other sources. Adequate topography is critical to hydrologic modeling, flood <br />inundation mapping efforts, and for web-based product dissemination. <br /> <br />· Soil Properties and Land Cover - The influence of different soil types and characteristics <br />and land cover should be reviewed and carefully taken into consideration in the statistical <br />analyses and hydrologic and hydraulic modeling. Changes over the course of the last century <br />may have significant impacts on expected runoff (comparing current present forestation with <br />earlier mining activities or the effects of wildfire). Detailed information is needed to <br />quantify inadvertent storage in upper basin for hydrologic modeling and statistical analyses. <br />This element is particularly necessary to help evaluate the processes of the 1938 storm and <br />flood and other early floods in the gauged record and implications to current flood generating <br />processes. <br /> <br />ANALYTICAL TOOLS NEEDED <br /> <br />· Rainfall Veriflcation - Compare rainfall data, obtained from coarse-scale 1973 NOAA <br />maps, with more recent detailed data collected in the South Boulder Creek watershed and <br />other areas along the front-range for verification. This should also be compared to other <br /> <br />I <br />