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The Texas Triangle is rapidly expanding and increasingly vulnerable to extreme rainfall and floods. Using the Weather Research and Forecasting model coupled with chemistry (WRF-Chem), we simulate a cold-season frontal storm and a prolonged warm-season event, comparing a present-day configuration with an end-of-century urban-expansion scenario consistent with Shared Socioeconomic Pathway 5 projections. Across scenarios, meteorological boundary conditions are held fixed, while urban land cover is expanded and anthropogenic emissions are enhanced accordingly. In the cold-season case, urban growth enhances activation of fine-mode cloud condensation nuclei, strengthens updrafts, and produces statistically significant precipitation increases over San Antonio and Austin. In the warm-season case, the response is heterogeneous, with early enhancement on the western side of Dallas-Fort Worth followed by suppression eastward as the system evolves. Flood-risk analysis, based on the model-diagnosed runoff coefficient and a high-resolution stochastic framework (SCS-CN), reveals a systematic expansion of high-risk zones under future urbanization, amplifying existing runoff hotspots and generating new ones across metropolitan areas. Overall, the consistency between the WRF-Chem runoff diagnostics and the stochastic SCS-CN framework supports the use of WRF-Chem as a first-order, spatially explicit indicator of relative urban flood risk under extreme precipitation.
Moraglia et al. (Thu,) studied this question.