Stormwater runoff is defined as rain or snowmelt that travels over impervious surfaces such as roadways, buildings, or parking lots, and landscaped or agricultural areas and is then collected and conveyed into streams, rivers, lakes, bays, or oceans. Upgrading large networks of aging systems underneath densely populated areas carries significant costs and engineering challenges. Many of the country’s legacy stormwater systems, are struggling with the high cost of retrofits needed to address urban flooding and climate change. With few dedicated funding sources, complicated governance and ownership structures, expansive networks of aging assets, increasingly stringent water quality regulations, and concerning climate change projections, the expected performance of stormwater systems is declining. Federal funding, though up in recent years, averages about $250 million annually, which leaves a growing annual funding gap of $8 billion just to comply with current regulations. Nearly 600,000 miles of rivers and streams and more than 13 million acres of lakes, reservoirs, and ponds are considered impaired. Stormwater also affects water quality as polluted runoff from pavement enters water bodies.
While stormwater utilities are on the rise, with more than 40 states having at least one, the impervious surfaces in cities and suburbs are also expanding, exacerbating urban flooding, which results in $9 billion in damages annually. Stormwater systems range from large concrete storm sewers, roadside ditches, and flood control reservoirs, to rain gardens and natural riverine systems.
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