A chain of rain gardens--reinventing stormwater channels

In response to a previous article, where I proposed a chain of rain gardens in the greenway, I received comments that led me to wonder if my proposal had been clear enough.  So here's another stab at describing the idea.

The "chain of rain gardens" concept is an attempt to reinvent how stormwater channels are designed.

In the past, stormwater channels have been straight, sterile, ugly, and built to last with little maintenance for a long, long time.  The old concept was to take the stormwater downstream as fast as possible.  But standards are changing fast, and it's time for Madison to design something better.

I'm proposing a simple alternative--rather than a channel, make a chain of connected pools.  The pools can be of whatever size that works.   Think of this concept as a cross between a regular storm channel and many rain gardens.  Or think of it as a chain of connected rain gardens that are reinforced on the sides and bottom to withstand floods.

Series of wetland pools created with the Deltalok soil-filled bags and locking plates, before and after growth of vegetation. 

More photos thanks to Deltalok.

The design needs to handle the two extremes of floods and keeping the plants healthy during dry spells (with rain barrels and soaker hoses).

Advantages of the chain of pools concept:  To...

• mimic the appearance of a natural stream
• slow the floodwaters
• create some pleasing variety
• incorporate native vegetation
• give wildlife a place to drink
• return water to the ground from lingering pools.

I'm not proposing a rain garden next to an old-style stormwater channel.   Instead, combine the two. 

And, I'm not proposing one giant rain garden to absorb all the floodwaters.  Whatever fits the space is OK with me!  Together, the chain of pools creates a larger rain garden.  The water in each pool will linger after a storm, slowly recharging the ground. 

Our greenway can benefit all Madisonians by being an "outdoor laboratory," where we can experiment with various kinds of plantings and reinforcement.

If engineers tell us there's no inexpensive alternative to dumping tons of rubble (called riprap) into the ravine, I'd counter by saying: "Let's take the challenge, and invent our own alternative."  I believe it can be done--Madison can be a leader.

I suspect that worries about maintenance may be holding us back from coming up with a better, more modern design.  Sure, riprap will last 100 years without maintenance. But what's wrong with a little maintenance?  We do it with buildings, with roads... with whatever we care about. So why can't a little maintenance be done on stormwater structures, especially if the result is something less expensive, more beautiful, and better for the environment?

In writing this blog, I've learned that green infrastructure is rapidly developing.  With such rapid progress, it doesn't make sense to build for a hundred years. Instead of a clunky, ugly design that will last forever, let's come up with a smart design that's lean and mean--just enough to prevent erosion; no more than is needed. 

Madison seems behind in the urban green revolution. This controversy isn't just about one greenway--it's the opening shot in an effort to lead Madison to a greener future.  It's an issue for all of Madison.

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Deltaloc bags restore a streambank in residential North Vancouver, Treetop La. Our climate is relatively harsh, but vegetation can be established with a sustained effort.

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The chain of rain gardens concept has already been tried in the Siskiyou Green Street Project in Portland, Oregon.