When Every Minute Counts: Decision Support for Compound Flooding

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Nina Reins

Water Resources Engineer

Second in a series

Guidance system predicting flooding on both storm surge and precipitation
The CFIGS system predicts flooding due to the combined influences of storm surge and precipitation. Its dynamic inundation graphics enable decision-makers to understand the timing and extent of flooding.

During a hurricane or tropical storm, one of the biggest threats to communities is compound flooding from storm surge and precipitation. Forecasting storm surge and riverine flooding in real times, however, is incredibly challenging — especially along Louisiana’s complex coastline. Our multidiscipline team is addressing this challenge by providing Louisiana’s decision-makers with flood guidance in real time. With a 15-year track record of proven success, our team deploys supercomputer-powered models to rapidly inform critical decisions at a large scale.

The Compound Flood Inundation Guidance System (CFIGS) provides decision support to state agencies using 2D HEC-RAS models along with real-time rainfall and coastal water levels (including storm surge from tropical cyclones) from the ADCIRC Surge Guidance System (ASGS).

The guidance is available on the CERA website to provide decision support and emergency response for flooding similar to August 2016, storms like Hurricane Isaac (2012), or a combination of the two, all unified in a single web interface.

Because the system is based on the distinctive aspects of a particular storm while it is forming, it provides more accurate forecasts than a probabilistic analysis of many past storms. Additionally, it can inform decision-makers  about alternate scenarios, forecasting what would happen if a storm’s intensity were to increase or if the storm were to change course and make landfall elsewhere.

About Our Team

At the heart of this work is the decision support tool developed and coded by senior hydrologist Katelyn Costanza, PE, CFM, the owner of CE Hydro, LLC, a Louisiana-founded woman-owned small business. Robert Twilley, at Louisiana Sea Grant, has been a key collaborator and supporter of this effort. Highly specialized hydraulic modeling resources from Freese and Nichols, led by Jim Keith, PE, CFM, and Bethany Fleitman, PE, CFM, have provided riverine modeling support to update, calibrate and validate a 2D model of the Lake Pontchartrain and Lake Maurepas watersheds. In addition, team member Jason Fleming, Principal of Seahorse Coastal Consulting, is the lead of the real-time ADCIRC Surge Guidance System (ASGS) for Louisiana and integrates critical surge data, while Carola Kaiser at the LSU Center for Computation and Technology led the development of visualization tools for the real-time forecasts on the Coastal Emergency Risks Assessment (CERA) website. The work is being done for the Louisiana Coastal Protection and Restoration Authority (CPRA) and Louisiana Sea Grant.

Read more from the LSU Office of Research & Economic Development: Partnerships Improve Hurricane Storm Surge Forecasts for Louisiana, Nation

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Nina Reins, PhD, PE, PMP, is a senior coastal project manager in New Orleans.

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