A Flood-Ready Garden

This morning, Sustainable Princeton will host another in its excellent series of Great Ideas Breakfasts at the Princeton Public Library. This month's program is about water that comes through Princeton in all its forms: precipitation, runoff, drinking water, wastewater. I'll be leading one of the discussion groups, on the concept of resilient landscapes. Below are some photos of the stream that flows through my backyard during heavy, extended rains, and how I've harnessed that water to drive a productive and diverse habitat of native floodplain wildflowers, sedges, and (my daughter's contribution) ducks.

The water cometh from uphill.

In its path lies this normally tranquil scene, with a series of miniponds, a constructed stream channel, native sedges, rushes, and wildflowers building towards summer blooms, and a chicken.

After heavy rain falls steadily for a day or so, upstream soils become saturated and begin to shed any additional rainfall. The water begins to flow in from uphill neighbors' yards, bringing this ephemeral stream to life. When the rains stop, the plants will emerge unharmed and replenished, and a little of the runoff will have been held back, slowed down, by the series of check dams and miniponds.

Now looking towards the back of the property, a quiet "before" scene: our path to a little town park bordering our yard.

And a "during" scene, as rainwater runoff flows from the park into our yard, and gets redirected by a berm so that it will feed our ponds and then flow safely between two houses just down the slope from us.

Being ready to accommodate a flood also better prepares a yard for droughts. Slowing the water down allows an underground reservoir of moisture to form, sustaining trees and wildflowers through the dry times.

A "fillable, spillable" pond prototype--something of a mockup intended to give the ducks a place to swim during droughts. And, when the ducks have mucked it up the way ducks do, or when the mosquito wigglers appear, it can be easily tipped to spill and refill with clean water. Need to build a rock wall ramp on either side to provide ornament and also a means for the ducks to waddle up into the water.

The ducks love the heavy rains.

The chickens? Not so much.

Frontyard Raingarden

Every homeowner has to deal with drainage, which could be considered dull if it didn't stir considerable passions in people, particularly those on the receiving end of someone else's runoff.

The traditional approach has been to either ignore runoff until it causes trouble, or to get rid of it as quickly as possible, typically through buried pipes.

My approach is to make runoff the central driver in landscaping decisions, to treat it as an asset while keeping it away from the house, and to take as much advantage of it as possible before it leaves the property.

One dilemma in our yard has been that much of the rainwater from the roof was directed into the driveway via underground pipes. From there, it was expected to flow away through a small drainage pipe that has never worked very well. The drain has become so slow, and unrotorootable, that the driveway now behaves like a retention basin. Not a bad use for a driveway, in some respects, but not ideal.

Part of the solution has been to reroute runoff into the front and back yards, away from the driveway.

The most recent rerouting takes runoff from the front portion of the roof under a walkway and out towards the street. Given how little fun it is to dig under a walkway, this project was mulled over for many months.

Sure enough, digging a ditch has not gotten any easier since the last time. It's always good to have a spot picked out for the extra dirt, which in this case fortified the Maginot Berm that diverts runoff from my uphill neighbor's driveway away from our house and into another raingarden in the front yard.

One less than optimal aspect, not considered until after the fact, was that quite a few tree roots got cut in the process. A lawn's monocrop appearance gives no clue to the web of tree roots just below the surface. Hopefully the trees will end up benefitting from the extra water coming their way.

Chunks of sod got flipped upside down and put back in the ditch, then buried with loose dirt. Tubing had been previously obtained from the neighborhood curbside kmart before it could head to the landfill.

Some leaf compost from the Lawrenceville Ecological Center probably wasn't necessary, but a little doesn't hurt. Many native plants do fine in poor soil, and since this raingarden overflows across the sidewalk and into the street, it's best to minimize nutrients.

Here it is in action, holding water that will seep into the ground over the next day. Plants include soft rush, turtlehead, monkey flower, a Carex sedge, and a few other plants thinned from backyard gardens.

Diverting a Neighbor's Runoff Away From the House

During heavy downpours like yesterday's, water from my neighbor's driveway used to head straight for my house. This flow of water from one property into another is a common source of tension between neighbors.

Rather than complain, I dumped some extra dirt under some bushes on that side of my yard, forming a berm that redirects the neighbor's water towards the front of my lot. The water flows into a raingarden under the dogwood tree, where a buried, perforated pipe carries any unabsorbed water out to the sidewalk.

It's subtle, but you may be able to see the water flowing across the sidewalk into the row of hostas.

The goals here are 1) divert water away from my foundation, to reduce humidity in the basement, 2) capture some runoff in a raingarden so it has time to infiltrate into the ground to feed the trees, 3) use the city stormwater system in the street as an escape valve for any extra water the raingarden can't hold.

The only drawback is that, if you want to have the satisfaction of seeing that the system works, you have to go out in the rain, which, after the lightning and thunder has passed over, may not feel like a drawback at all.