How to deal with a coincident storm surge and rainfall in a community

Having boots on the ground or developing a mathematical model to simulate the flood event can help communities deal with flooding from a surge storm and heavy rainfall that occur at the same time.

By Rahul Parab, Dewberry July 6, 2018

When dealing with a coincident storm surge or high tide and rainfall in a community, there are two ways to effectively address the problem.

1. Boots on the ground during the event

The best way is to be on the ground to see what happens during the event. You should find locations to observe where the flooding spots are within a community, how much flooding occurs, what time it occurs and what the potential damages are during the event. A word of caution-make sure you are in a safe position to observe the effects of the event. Otherwise, let the trained safety community officials do the job.

As it turns out, I had the chance to have boots on the ground during a high-intensity rainfall event which occurred during high tide within the City of Hoboken, New Jersey on in May 2015. I live near Hoboken, and I had a chance to experience the flooding first hand. The image below shows a car trapped by floodwaters during this rainfall event that lasted several hours. My field reconnaissance provided insight on various flooding locations within the City of Hoboken which we were able to be leverage for the Rebuild by Design – Hudson River project.

2. Develop an integrated coastal and stormwater mathematical model to simulate the flood event

A safer way to understand the flooding risk from the coastal and rainfall event without putting boots on the ground is to develop an integrated coastal and stormwater model that can simulate the dynamics of storm or a combined sewer system within a community during the event. Our New York office recently pioneered the development of an integrated model on several flood resilience projects in New York and New Jersey. The Rebuild by Design – Hudson River and Red Hook Integrated Flood Protection System projects are two great examples where we were able to develop these integrated models.

According to the New York City Department of Environmental Protection (NYCDEP), this integrated model is a pioneering and innovative application of the latest technology to really understand the hydrology, hydraulics, and hydrodynamics happening all at the same time during an event. The integrated model developed for the Red Hook Integrated Flood Protection System is the first of its kind of model, developed in New York and used potentially in the U.S., on post-Superstorm Sandy resilience projects and has spurred NYCDEP to invest in these types of model developments in New York City.

With the understanding of the existing flood risks, we developed a coastal flood resilience solution (referred to as IFPS) to prevent the intrusion of coastal storm surge into the community, which was then tested against similar storm conditions within the integrated model. The model results for this flood resilience solution shows reduction in flooding from a combined coastal storm surge and rainfall event.

Similarly, for the Rebuild by Design – Hudson River, we developed a detailed coastal hydrodynamic model to simulate Superstorm Sandy flooding. An integrated coastal flood resilience solution that blends with the urban fabric of the neighborhood was developed to prevent coastal storm surge flooding. We have developed and tested the effectiveness of stormwater management solutions on this project using the integrated modeling approach.

What’s the future of integrated modeling?

We are utilizing a similar integrated modeling approach on the Virginia Beach Sea Level Rise and Flood Analysis project. This project will provide the City of Virginia Beach with the most reliable information on its risks to coincident flooding and will help to develop effective solutions to minimize flooding risks.

With recent hurricane and nor’easter events in Texas, Florida, and Massachusetts, we believe this integrated coastal, stormwater, and riverine modeling technology will be effective to provide a holistic view of the potential concurrent flooding risks from an event within the community. Together, we can make our communities more resilient from future climate change.

Rahul Parab, associate, Dewberry, a CFE Media content partner. This article originally appeared on Dewberry’s blog.

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