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Flooding events are natural occurrences. However, a storm system as substantial as a hurricane can result in rare and historic rainfall totals, as seen recently with hurricane Harvey. Nederland, TX, for example, received more than 60 inches of rain from Harvey, setting a new record. Meanwhile, approximately 26 inches of rain fell from the storm over the course of a single day in Port Arthur, TX. When extensive rains, such as those just mentioned, are coupled with impervious surfaces prevalent in urban environments, the magnitude of a flood event may be exacerbated. Knowing this, how can we as a society establish necessary city infrastructure while simultaneously mitigating the potential impacts from flooding and major storm events? The answer largely involves watershed-scale planning and management.
A watershed is an area of land that water flows within on its way down gradient. More simply, a watershed may be thought of as a bathtub—only this bathtub could be the size of a city, county, or even multiple states. When rain falls within the imaginary bathtub it will flow down the sides of the bathtub and ultimately to the drain. In nature, the sides of the bathtub may be hills, the bottom of the bathtub a river, and the drain a lake or ocean. Any water that falls outside of the bathtub would be in an entirely different watershed. The purpose of watershed-scale planning and management is to account for all variables that influence the movement and quality of water throughout a given watershed. Therefore, watershed-scale planning and management is integral to approaching flood mitigation and storm preparedness from a holistic perspective.
Highlighting this watershed approach, Ward Ling, watershed coordinator for the Texas A&M AgriLife Extension Service, notes “It is crucial for us to understand and account for the factors capable of either compounding or mitigating the magnitude of a flood event so that we may plan accordingly for them to the best of our abilities.”
In fact, Texas A&M AgriLife Research & Extension has been working for years in the research, development, and implementation of best management practices, or BMPs. Examples of BMPs related to watershed-scale planning and management include actions taken to reduce sedimentation rates of flood control reservoirs, installation of pervious pavement systems to reduce rainwater runoff, and establishment of waste control programs aimed at reducing flood control structure failure rates by keeping them free of debris. Only a few BMPs have just been mentioned, and in brevity at that. In reality, a multitude of BMPs have been developed and tested, each of which may be selected and tailored to fit the needs of a given watershed.
“After BMPs are implemented within a watershed, they work together to collectively mitigate flooding within that watershed,” said Michael Kuitu, an AgriLife Extension program specialist. “Given that many BMPs are designed to give rainwater a place to go, slow down, and allow pollutants to fall out of suspension or be filtered by control structures, the quality of surface water bodies may be improved as well through the reduction of nonpoint source pollution”, Kuitu added.
In many ways, the relative importance of these concepts are iterated in Ling’s closing statement: “Stewarding our watersheds impacts our very lives, whether by protecting water quality or ourselves through keeping in mind large storm events such as hurricanes and floods.”
Because urban areas are dominated by surfaces that are impermeable (e.g. parking lots, streets, etc.), improving water infiltration into urban soils is an area where improvements could make an immediate impact.
Incorporation of low impact development (LID) concepts such as pervious pavers for parking areas, vegetative swales, bioswales, rain gardens, green roofs, other BMPs that slow down and treat water can make a big difference during and after flood events. For more information on LID and Green Infrastructure, click here.
