Use of 1D Unsteady HEC-RAS in a Coupled System for Compound Flood Modeling: North Carolina Case Study

Samuel T Bush,Randall L Kolar,Kendra M Dresback,Christine M Szpilka

doi:10.3390/jmse10030306

Samuel T Bush, Randall L Kolar + Show 2 more

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https://doi.org/10.3390/jmse10030306

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Abstract

The research presented herein develops and compares an ADCIRC and ADCIRC/HEC-RAS (1D) paired model for the purpose of compound flood modeling within the Tar River and Pamlico Sound basins of North Carolina. Both the ADCIRC and 1D HEC-RAS models are capable of simulating river systems but differ in their underlying numerical formulations. A case-study comparison of each model’s ability to simulate flooding accurately and quickly in a riverine/estuarine system is investigated herein; results may serve as a valuable reference to forecasters and model developers. Individual models of the Tar River and Pamlico Sound area in North Carolina were used, and pairings of these models were devised to determine the benefits and drawbacks of using ADCIRC alone, or ADCIRC + 1D HEC-RAS, to simulate the response of the Tar River and Pamlico Sound during three test events: Hurricane Irene, Hurricane Floyd, and an unnamed April 2003 event. With increased emphasis on predicting total water levels, the results of this study can provide information for the possible development of similarly paired models for coastal river systems across the US and improve the body of knowledge about each model’s relative performance in riverine and estuarine areas.

Highlights

Background and MotivationThe population of coastal watersheds around the United States (US) has been increasing over the last several years [1], and in 2010, as much as 3% of that population is living within the zones classified as 100-year coastal flood hazard areas [2]
The research presented in this paper looks to undertake a systematic comparison of several different coupling techniques: hydrologic, hydraulic river models, and hydrodynamic coastal models, as applied to the Tar River Basin in North Carolina
To compare the different coupling schemes and the differences between the HECRAS and ADvanced CIRCulation (ADCIRC) models, two tropical cyclones and a heavy precipitation event were examined within the North Carolina study area

Summary

Introduction

Background and MotivationThe population of coastal watersheds around the United States (US) has been increasing over the last several years [1], and in 2010, as much as 3% of that population is living within the zones classified as 100-year coastal flood hazard areas [2]. Total water level (which includes tides, waves, winds, and rainfall-runoff) modeling during tropical cyclone events, including estimates of freshwater rainfall-runoff, is critical for accurately predicting future flooding in coastal cities, as it pertains to long-term risk assessment [7]. In these coastal (riverine–estuarine) zones, there is a significant NOAA service gap regarding freshwater flows, i.e., significant freshwater flows in some coastal plains are not currently accounted for in many of the operational model forecasts [5,8]. Numerical prediction of flood stage in these riverine– estuarine areas represents a significant challenge due to the presence of compound flooding, defined to be synonymous with total water level modeling

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