Geospatial datasets and hydraulic model for flood-inundation maps for Rio Grande De Loiza in and near Caguas, Puerto Rico

Digital flood-inundation maps for a 2.7-mile reach of Rio Grande De Loiza in and near Caguas, Puerto Rico, were created by the U.S. Geological Survey (USGS) with funding from the U.S. Geological Survey Supplemental Oversight Team which received funding for this effort through Title VII of Division N in the Consolidated Appropriations Act, 2023 (Public Law 117–328). Flood profiles were computed for the stream reach by means of a one-dimensional step-backwater model. The model was calibrated to the current (rating number 30.1) stage-discharge relation at the U.S. Geological Survey streamgage Rio Grande De Loiza at Caguas, Puerto Rico (station number 50055000). The hydraulic model was then used to compute 16 total water-surface profiles for flood stages ranging from 19.00 ft to 34.00 ft. The overall range in stages are from “moderate flood stage” to above “major flood stage” as reported by the National Weather Service. The simulated water-surface profiles were then used in combination with a geographic information system digital elevation model derived from light detection and ranging data to delineate the areas flooded at each water level. The model produced by this study could be used to assess possible flood mitigation options and define flood hazard areas that could contribute to the protection of life and property. The availability of these maps, along with internet information regarding current stage from the USGS streamgage and forecasted high-flow stages from the National Weather Service, could provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for post-flood recovery efforts.