Stormwater Straight Talk: Stormwater management basics

  • Published
  • By 78th Civil Engineering Group

ROBINS AIR FORCE BASE, Ga -- Stormwater runoff consists of precipitation that falls on the ground and flows across the land to creeks, streams, rivers, lakes, and oceans. As roads and buildings are constructed, we must think about where the water is going to be conveyed when it flows through our built environment. This practice is generally referred to as “stormwater management.” In this Stormwater Straight Talk column, the prevention of pollutants that can be carried to our waterways in stormwater is often discussed.  In this article, managing the quantity of stormwater is discussed.  

The need or the technology to redirect millions of gallons of rainfall was not always necessary. In its undisturbed state, land manages water naturally. Vegetated areas absorb a portion of precipitation, and what is left over combines with runoff from steep or rocky areas to saturate wetlands or flow into local water bodies and eventually out to sea. Wetlands, which may also be present along the floodplains of water bodies, detain and absorb stormwater more slowly, naturally filtering some pollutants through plant root systems. According to the United States Geological Survey (USGS), the land area of the contiguous 48 states held over 220 acres of wetlands that helped to prevent flooding and erosion in the 1600s.  

Human development disrupts the natural flow of water. Less than half of the wetlands originally present in the United States remain. In their place, roads, buildings, and agricultural fields have been constructed. These surfaces alter the landscape from vegetation that would absorb water to something less pervious that will cause a greater volume of stormwater runoff to accumulate in the same amount of area. This runoff from impervious surfaces can concentrate into higher velocity and higher volume flows downstream, causing washout of vegetation and flooding, which impact the health of our water bodies and the safety of our built environment.  

Stormwater management systems are designed to mimic the functions of natural systems. Drainage and collection structures, such as storm drain inlets and channels, direct water streams to water bodies. Parks and green spaces allow for soil infiltration. Lakes, like Duck Lake, and detention and retention basins, like the basin near the entrance to the Air Force Reserve Center slow the flow of stormwater. Increasingly popular green infrastructure improvements, such as the bioretention basins in the parking lot of Building T549, hold and absorb water like wetlands. We are always finding new ways to work with nature to keep our built environment flood-free and our natural environment healthy!