Determining flood return periods using ArcGIS-based hydraulic modeling and observation: A case study of Schoharie Creek, New York.

摘要

In August 2011, Hurricane Irene swept through a large area in New York State, leaving thousands of people homeless and cities in pieces. The damages were widespread and devastating, whereas the precise scale of the floods is still unclear. The crucial part of modeling flood is to decide its return period, especially for the un-gauged areas. This research aims to model the flood inundation and decide the return period using HEC-RAS model, assisted by the GIS, incorporating multiple sources of data.;This research focuses on an area located in the Schoharie Creek Watershed between the towns of North Blenheim and Breakabeen, which was attacked by floods in Aug 28, 2011 due to high precipitation of Hurricane Irene. Both towns have U. S. Geological Survey (USGS) gauging stations. LiDAR data and aerial imagery using a Rochester Institute of Technology (RIT)/Information Products Laboratory for Emergency Response (IPLER) airborne multi-sensor platform called WASP (Wildfire Airborne Sensor Program) are collected two days after the flood event (Aug 30, 2011). HEC-RAS utilizes 10m National Elevation Dataset (NED) Digital Elevation Model (DEM) data, LiDAR data, National Land Cover Dataset (NLCD), and stream flow data from the two nearby USGS gauging stations as input parameters to conduct a series of model simulations. The aerial imagery is used for the validation. Then, the model results are paired with Federal Emergency Management Agency (FEMA) flood scenarios to find out the actual flood return period of the event, as well as the correspondence between the water stages and the flood extents. Lastly, a visualization of the flood is animated using Google Sketchup. The modeling process, once validated, can be applied as important reference instruction to guide the best management plans for the decision makers and stakeholders.;Key words: flood, modeling, HEC-RAS, GIS, return period, scenario, analysis