It has been raining pretty steadily for the last two days. I hear some areas south of us received 9 inches but we’re feeling that 3 or 4 is more than enough. As chance would have it, I spent about 8 hours today attending a conference about the use of native plants in urban spaces with a focus on using native plants to manage storm water, sponsored by the design firm EcoLogic.
“Alternative storm water management” was one of the key buzzphrases when I worked for JFNew as an engineering consultant a few years ago. It’s one of those ideas that makes a lot of sense but is totally opposite from conventional storm water management. Okay, so the old school way of dealing with storm water was to get it off-site and into a stream as quickly as possible. This makes a lot of sense if your main goal is to keep your building from flooding. However, it has several unfortunate consequences. One is that all the pollutants that get washed off roofs, streets, and other impervious surfaces get immediately dumped into our streams. The other is that a large amount of water gets dumped into streams all at once, which means the stream experiences higher flow levels than it would in a natural setting and there can be flooding downstream.
So the theory behind alternative storm water management is this: Why don’t we try to hold some of the water on-site and let it infiltrate into the ground the way it used to? This recharges the groundwater, it allows some of the pollutants to be filtered out as the water flows through the soil, and it helps the streams have a more natural flow pattern.
One of the most common ways to do this is using a bioretention area. The basic idea is to have a depression (dry pond) that captures water during storm events and then lets it percolate slowly into the ground. They can be done at a variety of different scales but someone wisely dubbed the backyard version “rain gardens.” Rain gardens are becoming much more common as a landscaping option for individual residences and are being actively promoted here in Monroe County. They’re pretty easy to build; you basically dig a depression in your yard that will naturally catch water, amend the soil a little bit so it will let water infiltrate (this is especially important in Bloomington where we have heavy clay soils), and plant some water-tolerant native plants.
Native prairie plants are ideal because they have massive root systems that help increase infiltration rates and they also are used to tolerating periods of extreme drought and extreme water. There are also lots of cool native wetland plants to use in the wettest part of the rain garden. I listened to a couple of botanists talk for two hours about what species are the most appropriate but really, the key is finding plants that will tolerate a wide range of moisture and that you and your neighbors agree are at least marginally attractive.
I think our landlord would frown on us digging holes in the turf grass that surrounds our little duplex so we’re going to wait on this one until we have our own space but I really want to build one. Maybe next year I’ll be ready for those April/March showers.