Flood Hydrograph Development Using Web Services for Data Access

Recent developments in hydraulic modeling programs, HEC-RAS in particular, have increased the popularity of 2D modeling in the industry. Two-dimensional hydraulic models improve the accuracy and flexibility of flood models, especially in complex situations. However, 2D models often require the use of an unsteady flood hydrograph for analysis of the study area. For this project, we developed a tool that accesses streamflow data from any user-specified USGS stream gage and then analyzes the annual peak flow values to produce a peak flow for a user-specified return period. Then, the peak value and SCS Unit Hydrograph ratios were used to produce a preliminary flood hydrograph of a user-given duration. Statistical analysis of the yearly maximum streamflows was performed using the guidance provided in the Bulletin #17B Guidelines for Determining Flood Flow Frequency, which employs a Log-Pearson Type III distribution technique for determining the peak flow. The Python script produced by this project creates a comma separated values (CSV) file for a preliminary flood hydrograph based on user-determined information that can be used in 2D modeling simulations.