Flooding is a result of stormwater run-off. Flooding increases as development covers the ground with impervious surfaces such as roads, parking lots, driveways, homes and commercial building. The ground can no longer soak up the rain.
As development in the Clear Lake area has increased over the past 40 years, so too have flooding issues. It isn’t just named storms like Tropical Storm Allison, Hurricane Harvey, and Tropical Storm Imelda that have caused flooding. Smaller storm systems, even “pop up” thunderstorms that can produce several inches of rain within a few hours have caused street flooding and even home damage.
Clear Lake’s location also increases the likelihood of heavy rainfall events. A hydrologist study commissioned by the Clear Lake City Water Authority (CLCWA) concluded that Clear Lake’s location in far southeast Harris County more closely parallel rainfall patterns of coastal counties such as Galveston and Brazoria Counties compared to the rest of Harris County, which is further inland.
As a result, Clear Lake has experienced eight 100-year flood events (13.5 inches of rain within a 24 hour period) since 1976, five 500-year flood events (19 inches of rain within a 24 hour period) since 1979, and one 5,000-year flood event (Hurricane Harvey in 2017).
Stormwater detention is becoming recognized as the best method to control flooding along the Upper Texas Gulf Coast. The goal of stormwater detention is to quickly drain the stormwater off the streets and other areas into large ponds. The ponds then gradually discharge to natural waterways.
Previously, the favored practice had been to make drainage waterways wider, deeper and straighter. The increasing urban development of the Upper Texas Gulf Coast has made this approach increasingly unaffordable by local jurisdictions and unsupportable by local communities.
The Exploration Green Master Plan
Most constructed stormwater detention basins tend to regular geometric shapes, such as squares or rectangles. The Clear lake City Water Authority (CLCWA) sought to create a system to five stormwater detention basins, sculpted to look like natural lakes. Each of the five detention lakes will hold approximately 100 million gallons of stormwater, or 500 million gallons/half a billion gallons total when complete.