Retention Pond compressedMuch has been made of floodplain development in Harris County. This topic is even more germane with the devastation of Hurricane Harvey on the Gulf Coast. Many have criticized the region’s insistence on developing “anywhere and everywhere.” Though, the arguments on that side seem cogent – the homes are built where the water flows – they are lacking some geological, ecological, and hydrological background.

Since its founding in 1836, Houston has always been a city without boundaries. Built on real estate, the city has worked hard to stifle restriction to growth. Because of this work, Houston has seen explosive development and population growth. This can be seen no better than in the western sections of the county as well as the southeastern sections of the county. These two areas have seen exponential growth in the last 60 years as industries have moved in and, in the case of Exxon, developed their own municipalities to house employees. These two areas were also heavily affected by flooding from Hurricane Harvey. The question we are going to ask is what can be done?

Following Hurricane Ike, researchers from Zheng Fang and other researchers from Rice University, the University of Illinois at Urbana-Champaign, and the University of Oklahoma performed a study to evaluate the effects of urban development on flood control storage. They used Cypress Creek in Northwest Harris County as their case study. In their study, they performed several tests: an upstream development, a midstream development, a downstream development, and a region with all three developments. Separately, each development had efficient runoff systems for a 100-year flood event, including detention ponds and a regional reservoir. Their findings showed, however, that the flooding culprit was not the lack of detention ponds but the existence of a midstream development.

Fang et.al. concluded that “detention regulations should be imposed with a knowledge of locations relative to watershed headwaters or a referenced outlet point (i.e., upstream, midstream or downstream).” To summarize their work, regional reservoirs are invaluable in mitigating flow when utilized with ponds and proper drainage avenues. Their most pressing recommendation, however, is the effects of a midstream development. The midstream development caused the downstream locations to experience much higher peak flows than any other scenarios resulting in flooding. This creates a need for a much larger reservoir than would normally be needed.

To conclude, developments in floodplains will always have risk of flooding. However, hydrological models can and should be utilized to offset this risk. They are more valuable than the 100-year floodplain maps as they use real-time data to arrive at their conclusions. Should floodplains be developed? Yes. The benefits greatly outweigh the risks in a floodplain development and, with proper drainage avenues and adequate flood storage size, this risk can be mitigated greatly.

For more information, contact:
Eric Schwartz, MAI, SRA, AI-GRS
Managing Director, Real Estate
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Phone 713.771.5011