Looking Forward:
Real-Time Flood Warning
and Flood Forecasting

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By Andy Yung, P.E., CFM

Floods are the most common and widespread natural disaster across the world (FEMA). Of the Presidential Disaster Declarations in the U.S. between 1953 and 2015, approximately half of them were a result of flooding events (riverine flooding, tropical storm surge, coastal storms, and dam/levee failure).

In the event of a flood, over half of all flood-related drowning deaths are vehicle-related (CDC). As a result, the need for flood risk reduction projects is high. However, many communities cannot afford to complete major flood control projects which typically cost hundreds of millions of dollars. As an interim or complementary component to flood control works, flood warning/forecast systems provide a tool which can assist communities in reducing loss of life and damages by providing advanced warning at a fraction of the cost of a major flood control project.

 

With an enhanced understanding of how serious a flood event may be, emergency managers can more adequately prepare the public for an emergency.

 

Several communities around the U.S. have gauging systems set up to collect rainfall depth and stream height measurements, but often these are used simply to monitor flood events in real-time. Flood “warning” coordinates monitoring data with emergency personnel and first responders to improve decision-making when issuing evacuation/shelter-in-place orders and/or roadway closures. Flood “forecasting” then takes warning to the next level by using algorithms or computer models to estimate future flood elevations and when maximum elevations are expected to occur.

Flood forecasting systems couple rainfall data with what is known about the response of a given stream system to such rainfall events and allows the user to look forward a few hours and ask, “How high is the flood water expected to rise?” Details related to flooding of critical elevations and lead time for emergency management operations are often added to these systems to optimize efficiency and reduce risk during a flood event. In addition, the mapping of inundation areas can be added as an output from these systems to assist first responders in identifying areas subject to the highest risk.

At the forefront of this technology is public safety. With an enhanced understanding of how serious a flood event may be, emergency managers can more adequately prepare the public for an emergency. Increased lead time and an understanding of areas most at risk will help the public make informed decisions regarding whether they need to evacuate, what route to take, whether to raise personal property to the second floor, move vehicles, avoid certain roadways, etc.

In the future, this technology will likely advance further with better data and technology and a better understanding of storm movement. This will result in better prediction of forecasted rainfall, which in turn will provide increased lead times for emergency personnel to issue warnings to the public.

With background in the development of protection systems and an understanding of the sensitivity to timing required to deploy protection measures, Walter P Moore has developed flood warning procedures for the Texas Medical Center and Houston’s Theater District. Over the past 15 years, Walter P Moore Water Resources has designed several flood warning systems, contracting with several public and private entities to develop technology which provides customized flood warning/forecasting systems in order to protect properties and assist those entities in protecting their properties while keeping the public safe. These efforts have involved partnerships with local agencies and research institutions, and innovative usage of cutting-edge forecasting and mapping models that are combined with algorithms developed in-house to better serve our clients in understanding both their flood risk as well as support their emergency operations during a flood event.

While flood warning/forecast systems are not a replacement for proper floodplain management practices, they are one important tool in a comprehensive floodplain management plan. They can be implemented while funding is being secured for other larger flood reduction measures. Flood warning/forecasting systems do not reduce flood potential, but they provide vital information to reduce flood damages, increase public safety, and improve the understanding of flood risk.