Advances in Flood Hydrology for Modeling High Elevation Mountain Basins in Colorado with Applications to the Gross Dam Enlargement Study

摘要

In Colorado's mountain terrain, traditional Probable Maximum Precipitation and flood hydrology approaches often result in spillway design floods that are perceived to be unreasonably large, ranging up to two orders of magnitude larger than floods of record. In this region traditional flood hydrology methods tend to over-estimate infiltration-excess runoff due to use of low infiltration rates and low surface retention losses. During Denver Water's 2017 site-specific hydrology study for their proposed Gross Dam enlargement, Colorado Dam Safety developed a model to account for interflow and saturation excess runoff mechanisms, which literature suggests are dominant processes for mountain basins. The model successfully simulated irregularities in hydrographs from the historic September 2013 floods. When applied to the Probable Maximum Flood, it simulated lower peak flows and volumes compared to a traditional flood hydrology model. Results suggest the new model better reproduces the dominant physical processes that occur in Colorado's mountain basins.