Using a Distributed Hydrologic Model to Evaluate the Location of Urban Development and Flood Control Storage

A physics-based, distributed hydrologic model (Vflo) was used to evaluate the effects of urbanization and detention storage on watershed stream flows with grid cells as small as 0.09 km2 (22 acres). The analysis was performed for the Little Cypress Creek watershed in Houston, Texas. Hypothetical development and flood mitigation scenarios in the upstream, midstream, and downstream portions of the creek were analyzed for their impacts on peak flows for the 100-year design storm. Local ponds and regional reservoirs were compared for their ability to bring downstream flows back to existing conditions at all points along the creek. Analysis showed that downstream flows would be most effectively mitigated when storm water detention volumes and release rates are imposed with an awareness of locations relative to watershed headwaters or a referenced outlet point. This is in contrast to many existing policies that are uniformly applied across a watershed.