Showing posts with label Stormwater. Show all posts
Showing posts with label Stormwater. Show all posts

Sunday, July 09, 2017

How To Rescue a Raingarden

It's doing better now. The blue vervain has rebounded impressively. After being mowed down for most of a year, the native grasses--big bluestem, wild rye, and switchgrass--had looked like gonners, but they too have reappeared in numbers and are reaching for the sky.

Most raingardens, like many Americans, lack medical insurance. There's no money to restore their health when the weeds take over. There's money to design them, and install them, and sometimes even regulations that require they be planted. But to keep them thriving and looking good? Well, they're pretty much on their own.

If you think about it, most urban landscapes are cared for by people who know next to nothing about plants. If the medical profession were run like the landscaping business, hospitals would be manned by custodians equipped with leaf blowers and weed whippers, and anyone who came in with a medical issue would be left to fester, then eventually mowed down when they became unsightly. Under such conditions, trees can survive, and some foundation shrubs, but if you're a plant that's neither tree nor shrub nor turfgrass, life could be short.

The landscape architect who designed this raingarden, in a parking lot a few blocks from my house, likely had considerable training, and hopefully makes a decent living, but the designer is long gone and the garden will only survive if it is maintained. Whoever maintains it must know and be able to recognize, at every stage of their growth, not only the intended plants the designer was familiar with, but also the many kinds of weeds that threaten to overwhelm the intended plants. There's no time to pull every last weed, so efficient maintenance requires knowing which weeds pose a serious threat to a balanced planting, and which are benign. And by the way, all the money was spent on design and installation. Nothing's left to pay the people who determine the plantings fate and need the greatest knowledge.

I should have intervened sooner. Instead, a few years ago, having urged those responsible, to no avail, to hire either me or someone else who could give the raingarden the skilled care it needed, I watched as the intended plants got overwhelmed by a bumper crop of 7 foot high pigweed and lambsquarters. The next year, the landscape crew noticed how weedy the raingarden had become, so they mowed it all down and started treating it like a lawn. That's the classic progression: garden to weeds to lawn. The lack of plant knowledge makes most landscape care like a light switch. There are two positions: on and off. You either let it grow "natural" or mow it down. No selective intervention. Our inner gardens, which is to say our bodies, are cared for by knowledgeable people, who provide skilled medical intervention if need be. Why not a raingarden? The answer is that people matter, while saving a raingarden, like saving a livable planet, is considered optional.

Strangely, I feel lucky. Yes, I'm putting in a half hour here and there of volunteer work because of a culture's disconnect with plants, but one thing I learned from my astronomer father was to make a project more interesting by thinking of it as an experiment. How dramatically will a neglected raingarden respond to a little TLC? How little time can be invested and still get a good result?

There's such pleasure--why don't others feel this?--in rescuing a garden like this. Multiple levels of restoration happen at the same time: beauty, diversity, ecological function. And then there's the strategy, like playing bridge--using finesse to gain the best results with the cards you're dealt, dealing with multiple variables as the drama plays out. A different strategy is applied to each kind of weed. This is wild gardening, not total control. Leave the daisy fleabane with its weedy form but attractive flower. It's not doing any harm and won't take over. Take advantage of last night's rain to pull otherwise stubborn weeds out of the softened earth. Find satisfaction in the ease of undercutting a dandelion with a shovel blade. Catch mugwort or Canada thistle early, before they have a chance to spread. Feel the deeply American frontier mix of wit and muscle, mind and body. Live the wisdom of a hand-me-down phrase like "a stitch in time saves nine."

Otherwise, you end up with large swaths smothered with bindweed,

or carpeted with crown vetch. These will take something more than a clean undercutting with a shovel.

The solitary lambsquarter poses no threat at this point, and could end up in a salad.

The amaranth is already some insect's salad.

The smartweed (Polygonum) could prove aggressive, but the Japanese beetles are doing a good job of weakening its spreading tendencies. May as well leave it for now.

Velvet leaf isn't doing any harm, and will likely be eclipsed as the intended plants gain dominance.

Pilewort and

horseweeds are native weeds that grow tall and gangly, contributing to a weedy look if left in.

The catnip is staying for the meantime, though as a mint it could prove aggressive.

The Queen Anne's Lace (the same species that makes the carrots we eat) is pretty, but I've seen it take over fields in the midwest. Maybe remove it after the flowers fade.

There's no perfection here, and no certainty that each decision is the right one, but the results have been heartening, with the original plantings showing more resiliency than expected.

Next time I'm walking the dog over that way, maybe I'll remember to take pruners to trim back the redbud. Perhaps it should be called "casual insistence", this integration of garden rescue into the fabric of one's life, pulling weeds every week or two while the dog waits patiently. There are a few of us in town hard-wired to care in this way, with inner clocks that say "time to go take a look", who find this sort of casually serious and seriously casual persistence with a garden to be satisfying. Perhaps someday more people, maybe even some professional landscape crews, will discover the pleasure, and fewer raingardens will be lost to the weeds.

In the meantime, breathe in the cool air of an early summer evening, and feel like a conductor molding nature's growth force into a symphony, orchestrating the comeback of a raingarden nearly lost to the world.

Monday, November 14, 2011

Big Changes Come to a Hidden Valley

 There's a hidden valley in Princeton that everyone drives by but no one sees. Just over this ridge is Washington Rd, with athletic fields beyond. Down to the left is Faculty Road and Carnegie Lake.

Despite being sandwiched between a busy road and Jadwin Gym, the valley's rich soil sustains old oaks, tupelo, beech and ash that reach improbable heights.

This year, big changes have come to this long-hidden valley. Approached from Faculty Road, stacks of boulders and heavy equipment suggest some sort of road construction.

 A pile of stumps looks less than auspicious.

Further up the valley, more boulders, bales of hay, and orange fencing.

Giant trees, some a yard thick, have been cut down. How could this be anything but bad news? But wait, this post is getting depressing, so let's start from the top of the valley and work our way down.

The valley, which is to say the remnant of valley that was never developed as campus, begins at the new bridge over Washington Road. In the distance is the new chemistry building and the football stadium.

Looking downhill from the bridge, a lovely little stream meanders peacefully down the valley.

Starting farther up towards Nassau Street, the stream runs underground through campus, then emerges (or "daylights") from a big pipe just below the bridge.

The water immediately encounters what looks like an olympic luge track, attractively armored with stones.

 Further down, the narrow channel flows through a broad floodplain.

All of this--the pleasing meanders, the floodplain for stormwater to spread out into, the series of riffles and little waterfalls over stones--is manmade.

Why would anyone want to remake a stream? After a hundred or two years of flash floods caused by all the impervious surface on campus, the stream channel had eroded the ground around it, and was threatening to undercut Washington Road (beyond the green fence on the right) if nothing was done.

Here's a portion of the old streambed, broad and ill-defined. More photos of the old streambed can be found in a post one year ago when members of the Princeton Environmental Commission were given a tour of the proposed project.

A group from Rutgers developed the plans. In this photo, you can see the hoses used for pumping water around the section of stream being worked on. The "V" of stones at the left is called a "cross-vein". Water flowing over the rocks converges to scour out a pool just below them. Pools, riffles, and a narrow stream bed to focus flow are all characteristics of a healthy stream.

The stacks of boulders, then, are materials used to direct water in such a way that the streambank will survive the flash flooding coming from the hardened landscape of campus.

Lots of digging is required to form an adequate floodplain to accommodate the massive infusions of water during storms. The disturbed areas will be restocked with native plants, and though they had to take down some large trees, many were spared.

So that gets us back to the downed trees. This section of white ash is 36 inches in diameter. I counted roughly 200 annual rings, which are caused by the alternation of light-colored fast spring growth followed by a darker band of slower growth later in the season. The tree, and others in the valley, standing or cut, could well date back to the Revolutionary War. Visitors to Mount Vernon may remember the giant white ash trees in the circular drive approaching the house.

 About 160 years back, this ash began to grow very slowly, as can be seen from the very narrow rings on the left. Perhaps it was shaded heavily by another tree, which apparently fell 120 years ago when the rings began to spread out again.

It is unsettling that such old trees have been cut down, and all the more remarkable that few even know about it in a town that loves and protects its trees. But there are extenuating circumstances, tradeoffs made, factors that mitigate, at least partially, the loss. Erosion from campus has been undermining some of the majestic trees, and this project is meant to reduce that erosion.

Time will tell if the trees that were saved will survive all the disturbance around them. Tree roots are very sensitive. And the carefully designed channel is not necessarily immune from the powerful erosive forces of repeated floods.

One useful pursuit at this point would be to study the rings of the fallen trees to see what they might tell us of Princeton's past.

I had recommended a pre-construction rescue of rare native plants like horsebalm, but the idea probably got lost in the mix. Not everyone has learned to make a distinction between rare wildflowers that have survived for centuries in a valley, and whatever natives one can buy in pots at a nursery.

I had also encouraged them to remove the Norway Maples (mottled green/yellow in this photo and next) that have invaded the valley, since the invasive maples are competing with the old growth natives, and their dense shade will threaten the newly planted natives over time.

Overall, though, there's reason to believe this stream restoration--rare in New Jersey--will validate its good intentions. The project leader spoke excitedly last year during the tour about how he hopes students will find the valley an attractive place to visit, rather than merely serving as a traditional shortcut for athletes heading to practice.

This long-sheltered space, with so many stories to tell of past centuries, is beginning a new chapter worth reading.

Monday, October 03, 2011

What to Do With Grass Clippings

This photo may not be worth a thousand words, but it started a nice conversation. It so happened that, during one of my ongoing documentations of the export of nutrients from Princeton's yards, the owner pulled in. I figured he'd think, "Oh, just another Princetonian photographing my beautiful grass clippings," but to my surprise he came over and expressed interest in knowing what was so interesting about two blobs of discarded green.

It seemed inauspicious to begin a conversation by saying there's a (unenforced) borough ordinance against putting grass clippings on the street, but a mutual interest in composting quickly emerged. I offered news that the county extension master gardeners recommend leaving grass clippings on the lawn, so that all the clippings' nitrogen returns to the soil rather than getting washed down the street into Carnegie Lake. The dreaded thatch buildup of yore, which once spurred homeowners to bag up grass clippings, apparently dissolved into a myth.

Grass clippings' high nitrogen content endows them with the power to do great good or considerable harm. Massing them in piles tilts them towards harm. They pack tightly, shutting out oxygen, thereby making perfect habitat for anaerobic bacteria to feast on the rich organic matter. Break open a pile of grass clippings that have been sitting for awhile, and you will learn the hard way that the anaerobic decomposition process produces vapors profoundly repellent to humans. Aerobic bacteria, by contrast, do not produce nasty odors. Therefore, the best thing to do with grass clippings, if one is determined not to leave them on the lawn, is to give them access to air by spreading them in a thin layer either on a compost pile or as a thin mulch under shrubs.

Particularly relevant this time of year, autumn leaves, chopped up as one's mowing the lawn, can also be left to settle down into the ground between the grass blades.

Sunday, August 28, 2011

Princeton High School Floods Again

Yesterday, with Hurricane Irene headed our way, I stopped by the Princeton High School to check on preparations for the coming deluge. This part of the school had stormwater seep under the doors a week ago, and was most emphatically flooded two years prior when Hurricane Bill paid a visit. I've heard from several sources that the bill for Hurricane Bill included a new stage floor for the high school's performing arts center, which had become warped by flooding damage. Even if insurance paid for the replacement, one has to wonder if the district school's insurance rates took a jump afterwards.

Here's how the flooding happens: The retention basin in the photo (a.k.a. "ecolab", which we have planted with native wetland species), is surrounded on three sides by the high school and receives runoff from the high school roofs and also from nearby parking lots. The basin in turn drains into the system of stormwater pipes underneath Walnut Street. If it rains long enough and hard enough, however, the street's underground stormdrain system becomes filled to the brim, water has nowhere to go, and the basin overflows. At that point, pipes no longer matter and surface flow dictates where floodwater goes. Since water flows downhill, the only way to get rid of the water is for it to flow out to Walnut Street and safely away from the building. Unfortunately, Walnut Street is higher than the high school doorway thresholds. In these heavy rains, Walnut Street floods and becomes a river, and stormwater actually flows towards the high school rather than away.

The highschool has responded to this by placing sandbags in front of all the doorways during heavy rains. These help, but when I stopped by at 1am this morning, after Irene's fury had begun to ease, the music room and hallway into the performing arts center showed signs of having again been flooded. (These photos were taken this morning, after stormwater had receded.)

Exasperated school staff were trying to pump water out of the school. The custodians had just finished prepping all the floors for the return of students, and now they would have to do it all over again. The cafeteria had flooded, and it looked like utility rooms in the basement were now under water.

One staff member tried to blame the vegetation in the retention basin, but all around him was evidence that the vegetation had played no role in the flooding whatsoever.

The drain, photographed this morning, showed no signs of blockage, which is no surprise given that, when the street storm drains become overwhelmed, the water reverses flow and heads in to the retention basin from the street, rather than out.
At 1am this morning, this whole area was a lake.
A curb cut meant to carry surface water away from the retention basin was instead carrying water towards it.
The only solution I see is to lower the curb on the other side of Walnut Street so that the mighty Walnut Street River can flow into the field owned by Westminster Conservatory.

This, in fact, is what some water was doing last night, but to an insufficient extent.
A pond formed in this field last night, next to the Westminster parking lot. Last year, the field was declared by Westminster's own consultants to be a wetland that could not be developed. Since the conservatory uses the highschool performing arts center for some of its performances, utilizing this field more effectively to prevent flooding of the high school seems to be a solution that would benefit all involved.

What needs to be made clear to decision-makers is that the native plantings in the retention basin have no impact on flooding, lest this ecologically vibrant and educational planting become the victim of an invasion of red herring.

Hurricane Irene--A Reprise of Hurricane Bill's Flooding Two Years Prior

Most of these photos are from a post two years ago after Hurricane Bill paid a visit to Princeton. Hurricane Irene, because it passed through 'round midnight last night, was less photogenic, but the impact of the torrential rains was the same. The underground pipes designed to carry away stormwater get overwhelmed, the streets become rivers, and the flow of the water becomes dictated by the lay of the land (and streets).

In my part of town, these massive downpours cause water to flow from the high school and Westminster Conservatory onto Franklin Street. It then takes a right down Ewing before making an unfortunate left turn into the apartment parking lot.

The water then flows pell mell down to the bottom of the parking lot, (photo taken today, after flooding was over)

quickly overwhelms the stormdrain, then heads under the fence into people's backyards.

This is not good. The water came within one inch of the neighbor's threshold.

After flowing diagonally across the block through backyards and around foundations, it emerges across the street from me, spilling over the curb at Ewing and Harrison Street on its way down to the intersection with Hamilton, where it serves as a traffic calming device.

Back at the point where things go wrong on Ewing Street, this unfortunate foray of stormwater runoff into people's backyards could be avoided if the entryway to the apartment parking lot off Ewing Street was raised slightly so that the surface water would continue down Ewing rather than flow into the parking lot.

I proposed this solution to the borough engineer two years ago, to no avail. Reportedly, the borough has no control of the matter, and the apartment complex is within its rights to (unintentionally) "harvest" stormwater from a public street and divert it into the yards of neighbors.

All this seems strange. Since the needed modification is within the boundaries of the borough's street right of way (the street right of way actually includes the sidewalks), the borough would seem within its rights to intervene. In the meantime, history continues to repeat itself.