Floodplain Mapping of Ungauged Watershed Using HEC Models and PERSIANN Precipitation

The study develops the framework for simulating rainfall-runoff in an ungauged watershed using satellite precipitation products and develops a floodplain map. The combined effects of urbanization and climate change have led to an increase in flooding incidents during the past decades. For policymakers and system managers to make the watershed resilient during extreme flooding events, where even minor creeks are generating urban flooding and whose watershed has no meteorological station, the precise prediction of the flood-prone zone is essential. Rainfall and runoff data sets are essential for hydrologic and hydraulic analysis to develop flood-prone zones. This work applies satellite precipitation products that are extracted with the aid of Python code in a hydrologic model to develop runoff and makes use of generated runoff in a hydraulic model to develop a flood-prone zone in an ungauged watershed. To simulate and model interactions between rainfall, runoff, and the extent of the flood zone in the proposed study region, the Hydrologic Engineering Center-River Analysis System (HEC-RAS) and Hydrologic Modeling System (HEC-HMS) models are used. The first phase involves setting up and calibrating the HEC-HMS model using a satellite precipitation product. In the second phase, three simulation types are run in the calibrated HEC-HMS model with 25, 50, and 100 years of rainfall return periods to produce the hydrograph during the corresponding precipitation occurrences. Finally, a 1-D HEC-RAS model using the obtained peak hydrograph is used to create a flood inundation map for the relevant flooding episodes. The created flood map shows the impacted area during various return periods of flooding occurrences as well as a quantified depiction of inundation extent percentage (IE%) by comparing the values of the specified return periods.