Flood plain delineation for the Fremont River and Bull Creek, Hanksville, Utah

Predicted inundation maps for the Fremont River and Bull Creek in Hanksville, Utah, were developed using one-dimensional hydraulic models. Estimates of the 1-percent chance (100-year) peak streamflows were determined for the Fremont River and Bull Creek study reaches by using annual peak series data from streamflow-gaging stations and regional peak-flow regression equations. Surveyed topographic data for the study reaches were processed for use in the one-dimensional hydraulic models. The 1-percent chance (100-year) peak streamflows were simulated with hydraulic models to obtain predicted water-surface elevations. Water-surface elevations were then used to map the predicted inundation on a recent aerial photograph. The 1-percent chance (100-year) flood plain for the Fremont River in Hanksville, Utah, included some agricultural lands and did not encroach upon the town. The 1-percent chance (100-year) flood plain on the west side of Bull Creek was found to include a large portion of the town of Hanksville, Utah.