Generally speaking, parking lots don't absorb a lot of rainfall. Instead, the water is either directed into a retention pond or into the nearest gutter and eventually goes into the local water treatment system. The influx of water, even from light rain, puts extra stress on the already taxed infrastructure.
But there could be a better way, according to Brian Wamsley. He's a senior planner for Hamilton County Planning and Development, and is working on an idea to direct some stormwater runoff away from treatment plants. “This is a $2 to $3 billion infrastructure problem that we have to address,” he says.
He wants to transform parking lots from deserts into oases.
Wamsley says trees absorb a lot of water. A tree can drink in up to 100 gallons of water a day through its root system. The water is then returned to the atmosphere through the leaves, in a process called transpiration. He says a few trees doing that can make a big difference in the amount of storm runoff.
Some parking lots already have trees. But Wamsley says the design of the concrete islands doesn’t lend itself to keeping the trees alive. A tree that can live up to 150 years in nature will often only live for 15 years in a parking lot island because of the concrete curbs that surround the tree. “So what I am looking to do through codes is to find a way to use those islands to be depressed to absorb stormwater to give those trees a chance at survivability,” he says.
Wamsley says by redesigning tree islands in parking lots, the trees will live longer and absorb more water. He says the depressions would still need curbs around them to keep cars and snowplows out, but they’d have channels cut into them so water could flow to the trees.
Wamsley presented his proposals at the OKI Regional Planning Forum Friday morning.