Urban Flooding and Future Climate: Case Studies in Oklahoma and Texas

Urban flooding is a devastating natural hazard that affects cities globally and is expected to become worse in the future. To this end, techniques that enable planners and decision makers with more accurate ways to gauge the severity of flood events are key to adaptive planning and management. This presentation addresses research undertaken by faculty at the University of Oklahoma to model and simulate current and projected flood events in five urban watersheds in the cities of Oklahoma City and Tulsa, OK and Austin, Dallas, and Houston, TX. For each of the five urban watersheds, the presentation will discuss the development of site-specific flood models, their visual simulation, and the responses of urban floodplain managers to a Web-based survey used to determine the technique's appeal for future use.

The Vflo hydrologic model was used to perform watershed modeling for the target basins. Vflo is a distributed hydrologic model that integrates topography, land-use, soils, and imperviousness to calculate distributed flow rates and inundation depths. After incorporating a series of projected climate futures for estimating precipitation, two different precipitation inputs were used to determine the historical and future climate as input to the Vflo model for the target watersheds. Hydrologic simulations were then performed for each of the climate scenarios to determine the flood depths throughout the watershed. Simulations were calculated for the historical climate of each target watershed. The flow rates for the historical climate were compared with the FEMA effective flood insurance study (FIS) flow rates for each watershed. Model parameters were then adjusted to replicate the FIS flow rates. Inundation was then calculated using the flood depths determined from the watershed modeling at a high resolution that were subsequently used for watershed animations. The inundation extent for the historical 100-yr event was then compared with FEMA FIS inundation extent to verify that the inundation is reasonable. Finally, the inundation extent for the future 100-yr event was calculated and used to show the potential impact of future climate on the inundation extent.

To determine the acceptability and appeal of the technique, Web-based watershed surveys incorporating the visualized model simulations were prepared with Qualtrics software and initially presented to the urban floodplain managers for their review and comment. Upon revision, the surveys were distributed to a small number of watershed stakeholders in each of the case study watersheds.