Princeton University Stream Restoration--Part 2

Down in the valley, between Faculty Drive and Carnegie Lake, near Washington Road, the geese graze peacefully in the meadow, like a flock of pygmy long-neck dinosaurs.

Just across Faculty Drive, a new landscape has been hewn out of what I vaguely remember being a dense patch of scrub near the road. Not sure what the solar panel's for, but it's a nice modern touch.

This is the bottom reach added to the stream restoration since a previous post. The relatively steep slope allows a nice series of "cross-vein" structures (boulders assembled into the shape of a "v" pointed upstream, designed to focus flow inwards towards the center of the channel.) In the background, through the woods, are Jadwin Gym on the right and the new chemistry building back to the left.

On either side of the narrow channel are floodplains designed to allow floodwaters to spread out, slow down and thereby dissipate their energy, as would happen in a natural stream. Less energy means less erosion, which means less sediment flowing into Lake Carnegie, which in turn theoretically means the lake needs to be dredged less often.

Urban streams tend to get badly eroded over the years by the powerful blasts of flashy runoff coming from hardened surfaces in town. A stream restoration such as this attempts to mend the stream, designing in the right amount of meander, floodplain and well-placed rock formations so that it will resist deformation by the erosive force of all that heavy water coming down the hill.

Assisting in this goal to some extent are some absorbent green roofs and rain gardens installed in new buildings upstream. The tree trunks scattered in the floodplain probably play some role in slowing or redirecting floodwater.

The sewer (or maybe water) line looks like it will have a bridge mounted on it, so that athletes can cut through the woods to get to the playing fields.

Looking back down the slope towards Faculty Drive, with geese and Carnegie Lake in the distance. The matting spread over the floodplain should prevent erosion of the freshly contoured soil until grass seed can sprout through it.

The Story of STRAW

I was asked to speak at the public library this past Saturday after a showing of the inspiring documentary, The Story of STRAW. Contrary to the appearance of the title, the film does not describe how grass stalks are baled, but instead tells the story of how a classroom of kids and devoted teachers changed the fate of an endangered freshwater shrimp in a California watershed. The shrimp had fallen on hard times because their stream habitat had become degraded over time. Where once there were trees to hold the soil, shade the water, and offer exposed underwater roots for the shrimp to hide among, there were now cows tromping up and down eroded banks to graze on the grass.

Out of a young student's simple question, "What can we do?", was born Students and Teachers Restoring A Watershed. Working with ranchers, they fenced off the stream and planted willows along some 20 miles. The willows grew into a wooded corridor to protect the stream, shrimp numbers rebounded, birds and other wildlife returned to the watershed, and the group won a prestigious prize. An effort, apparently successful, was made to incorporate the work into the school's curriculum, boding well for the program's longevity.

The film brought back memories of one my first formative environmental experiences. A few times as a kid, I talked my dad into driving me to various streams to fish. Each time, the vision in my mind was of a healthy stream packed with smallmouth bass. What we encountered instead were textbook cases of environmental degradation and the destructive impact of invasive species. A waterway called Turtle Creek, for instance, looked promising on the map, but when we arrived, we found a muddy stream flowing through a cow pasture. Carp had taken the place of smallmouth bass. That creek, and I'm sure many others in Wisconsin's dairyland at that time, were in need of the same restoration STRAW was able to bring about in their California watershed.

A compelling vision of healthy ecosystems drives most anyone who finds themselves cutting down invasive shrubs or hauling water down a path to newly planted trees. It's a challenge, however, to translate the movie's appealing message of reforestation to the realities of Princeton's open space. The work of reforesting Princeton's cow pastures was done decades ago by the trees themselves, when most of the farms were left to go fallow. Human effort has been channeled into saving the land from development--work that began at least 40 years ago and continues to this day.

The restoration needing to be done involves not the sort of reforestation that makes for dramatic before and after photos, but a more subtle reestablishment of non-woody plants--wildflowers, grasses and so forth--that were obliterated by the plow and have not made as successful a return as the trees.

The locations in Princeton most like the pastures in the movie are retention basins--those curious looking turfy hollows carved out to catch runoff from developments. They offer a nice clean slate into which can be planted the many native species that like wet, sunny locations. Two of these--one at the Princeton High School, the other below the soccer fields at Farmview Fields on the Great Road--we've successfully transformed from turf over to native habitat.

Another inspirational project of this sort, that like the movie includes a great deal of participation by children, is in Ann Arbor, MI, where a vast swath of unused turf in an urban park was recontoured to catch runoff and host a rich assortment of native wildflowers, grasses and sedges. Prescribed burns make for an elegant and safely executed means of cleaning the plantings up each spring.

Radical Change Comes To Hidden Valley

There's a small valley in the middle of Princeton, unseen though thousands pass close by every day. The  stream, its channel badly eroded over time by stormwater from the hardened campus landscape, underwent an elaborate restoration (previous posts here and here),with boulders set in specific configurations to make a series of pools and riffles.

In contrast to most of Princeton's forests, which grew up on agricultural lands abandoned as recently as the 1960s, this valley's beeches, oaks, tupelos and white ash are nearly 200 years old. A few were sacrificed to reconfigure the stream and make room for the big equipment necessary to place the boulders in position, but many remained,

that is, until Hurricane Sandy came along. The nicely crafted stream channel is now clogged with fallen trees. If left uncleared, the trees will divert flow away from the carefully engineered channel.

I counted some twenty mature trees down, reminiscent of Pearl Harbor's battleship row after the Japanese bombing in 1941.

Included in the carnage were some of the giant old trees, their extensive, healthy root systems no match for winds that may well have been 20 mph faster than anything these trees had been exposed to in the past.

One theory I have, which may or may not be valid, is that the winds were not only stronger but also came from a somewhat different angle than our forests have been exposed to before. In this google map photo, the blue meandering line marks the hidden valley (next to Washington Road), and the purple line marks the direction of the hurricane winds, which being from the east had an unhindered path on Carnegie Lake to gain speed before slamming into the valley. It's also possible that the curved roof of Jadwin Gym (the white object above the tip of the purple arrow) served like the airfoil of a plane's wing to increase the wind velocity.

The few gaps in the canopy made by the stream restoration have now expanded, increasing the future exposure for those trees that remain.

Many young trees--this is a beech tree-were planted as part of the restoration. A more mixed-age forest should take shape over time. The trees will be cut away from the channel, and the hidden valley will still have its beautiful aspects. We can still admire the great trees left standing.

But the loss of so many grand, old, and still very healthy trees may be a local example of what is happening worldwide, as the radicalization of weather exposes forests to conditions they have not had time to adapt to. Seldom mentioned in discussions of changing climate is the extraordinary speed with which the human-caused changes are occurring. What might have happened over tens of thousands of years is now coming to pass in a century. In what has been lost here, it's hard not to see a warning. The more we cling to the status quo, the more the world around us will change.

Trees On the March

Something's going on in the field down next to Faculty Drive, across Washington Road from the boathouse at Carnegie Lake.

The troops are assembled, like high-stepping Clydsdales poised for the Arbor Day parade. Ready, forward, march!

But where to? The man assigned to water these 20 foot tall specimens said they're all headed into the woods to grow in the shadow of their granddad's generation, just across Faculty Drive, where the university is finishing up its stream restoration in the valley next to the new Chemistry building. (To see a history of the project, type "stream" into the search box at the upper left corner of this website). The university had to take down a few big trees last year (some possibly 200 years old) as part of the restoration of the heavily eroded stream corridor, and looks determined to give their replacements a head start.

The stream restoration is extraordinary in terms of how they created a lovely and hopefully durable streambed, but the botanical side of the project would have been more enlightened if it had included rescue of high quality native wildflowers prior to construction, and invasive species removal on the adjacent slopes.

And though they're putting in the same species of trees they took out--tupelo, pin oak and white ash--the chances the white ash in this photo will survive for more than a decade are pretty remote, given the near certain arrival in coming years of the exotic Emerald Ash Borer now spreading eastward through Pennsylvania.

I was craning my neck to see the thick, paired twigs that identify the tree as an ash, when I realized I could just look at the tag.

Walking a Stream in Herrontown Woods

The main stream at Herrontown Woods is probably the cleanest in Princeton, thanks to the Veblens
original gift of land, and the champions of open space who followed, ultimately preserving this stream's headwaters. More photos at the Friends of Herrontown Woods website: Soul Made of Wood, Rocks, and Water.

Many boulders bear the shells of hickory nuts, as if squirrels find the stream a good place to picnic.

Unclogging a Stream at Mountain Lakes

Clark Lennon, board member with Friends of Princeton Open Space and volunteer extraordinaire, is especially involved with clearing and maintaining trails at Mountain Lakes.

On this day, I talked him into helping expedite not only the flow of hikers and joggers in Mountian Lakes, but also the flow of water down one of the brooks just upstream of the lakes. The fallen trees were obstructing storm flows that could undermine the streambanks over time.

Bill Sachs and I pushed the cut logs up and out of the stream, leaving a clear channel. The little dam in the foreground suggests the spot was once a wading pool for residents of Mountain Lakes House.

The final result: a winding stream that looks like it's been that way for thousands of years. The work of restoring, like they say about good writing, doesn't call attention to itself. Unless, of course, someone brings along a camera.

A Birthday Climb Up Mount Tammany

What to do on a birthday? Wanting something more spiritual than material, we decided last month to climb a mountain. The best day to go turned out not to be my birthday but my sister Anne's, who had lost a battle with pancreatic cancer a couple years back. She loved mountains, and had climbed a few in her lifetime, the biggest being a figurative one--making it in the man's world of polymer chemistry. Towards the end of her career, she received a large grant to start an institute whose mission was in part to bring more women into the sciences. She loved gardens, modern art, and hard work, and took the long view--all good reasons to spend her birthday climbing a mountainside, with patches of dormant mountain laurel and blueberries telling of past bounty and future promise, and panoramic views to open our minds up wide.

In New Jersey, there are several mountains to choose from. Baldpate Mountain and the Sourlands close by, and High Point among others to the north. Pyramid Mountain with its improbable Tripod Rock sounded interesting, but we were warned the trails remained treacherous with ice. We ended up choosing Mount Tammany because it has the greatest rise, the steepest climb and the ranger thought the trails would be passable.

Even though well trod, there was enough snow and ice remaining that we had to step from rock to rock to get traction.

Last year's seedheads still hung on the mountain laurels.

There were small treasures, like the squiggly leaves of poverty oats grass,

and big, rewarding views.

If enough people gazed out upon a view like this, with one ridge giving way to another, on and on into the mist of infinity, America might take more interest in its shared future.

This shrub, growing in the rocky clearing at the top of the mountain,

is actually an oak.

After climbing up on the red trail, we took the blue trail over the ridge and down the other side, through a giant blueberry patch beneath an open canopy of oaks. I imagine that shade-grown coffee bears its fruit in a similarly filtered light in central America.

The hike down could have been treacherous if not for soft snow that gave more traction along the edges. On the hardened snow of the trail, finding a safe place to step required keeping an eye on the snow. Subtle variations in the light reflecting off the frozen surfaces hinted which snow would be the least slippery. Somehow during the descent, with each step requiring quick decisions, I found time to speculate on whether this ancient honing of eyesight for the sake of survival finds modern application in the appreciation of how light plays on a canvas or a photograph.

Linear etchings in the rock suggested past presence of glaciers.

One of the blue trail's rewards is a beautiful stream leading down a valley to the parking area.

Here's a good natural representation of what in stream restoration is called a cross vein. The rocks, shaped like a "V" pointing upstream, focus the water's flow inwards to create a scouring action that over time scours out a deep pool. Constructed examples of this can be found in Princeton University's stream restoration just down the hill from the new chemistry building.

Icicles of many shapes decorated the streambank, like frozen tears suspended above the water's flow.

Development May Threaten Tranquility of Herrontown Wood

There's a bit of a shock awaiting anyone who takes the short trail from the Herrontown Woods parking lot down to the rock-lined stream. Ribbons of different colors are now wrapped around trees; survey stakes mark points with significance unknown.

There's a strong feeling of invasion in a landscape thought to be safe from intrusion. Take a look at a map, however, and you see that what was assumed to be part of the park in fact is not. In the lower middle of the map is the parking lot, with a small portion of the driveway leading in at the bottom, to the right of "3.02". To the left, you can see that where the two streams meet is actually in a separate parcel. That long sleepy parcel of 10+ acres fronts on Snowden Lane across from Smoyer Park, and was recently purchased.

Thus far, I've contacted town staff and the Friends of Princeton Open Space. Stream buffer requirements (probably 50 feet on either side) may protect the space between the streams from development. The steep slope (evidenced by the topo lines being crowded together) may limit development in the upper left. But all of this is speculative, and doesn't rule out the possibility that one of Herrontown Woods' prettiest and most peaceful stream crossings could be compromised by housing construction.

Note: That trail, by the way, was blocked for a month or two by a fallen tree. Word got to volunteers Kurt Tazelaar and Sally Curtis, of Friends of Herrontown Woods, who spent a couple days clearing the blockage. If you like to "like", or want to read more about Herrontown Woods and the Friends group, check out the Friends' facebook page, and also various posts at VeblenHouse.org.

Below are the various ribbons and stakes encountered.

Stalking Monarchs, and Encountering the Other Milkweed Caterpillar

Note: This post serves as a contrast to the horrific flooding in Houston from Hurricane Harvey, showing how stormwater can drive diversity rather than destruction, if we work with nature rather than against it. Unlike cities, the plants that grow in floodplains are built to pop back up within days or hours after a flood and just keep on growing and flowering. Most of these photos were taken in a detention basin, which is an acre-sized depression in the ground, dug to receive storm runoff from the Smoyer Park parking lot. The purpose is to "detain" the rain that hits the asphalt and that would otherwise rush into the nearby stream. Detaining the water reduces flooding in downstream neighborhoods. The detained water then either seeps into the ground or is slowly released through a small pipe into the stream after the floods have receded. 

Last year, a collaboration of federal and local governments with the Friends of Herrontown Woods converted this mowed basin into a wet meadow with floodplain plant species that thrive with these periodic pulses of runoff. Without regulations requiring it, the concave setting for this lovely oasis for native plants and pollinators would not exist, and the polluted runoff from the parking lot would have flowed straight into the local stream, contributing to flash floods.

Nature has offered up some surprises, here in the doldrums of summer, when people who aren't somewhere else sometimes feel like they should be. There was the unexpected, and unexpectedly affecting, chance to capture family portraits of black vultures in the previous posts; the weather has been unexpectedly cool; rains have come when needed for the third year in a row, and monarchs have proved resilient, rebounding from their diminishing numbers in recent years. Not many, as yet, but more.

Thinking them elusive creatures, I figured a zoom lens was necessary to capture their image. First came a peekaboo shot on the far side of a thistle at the Smoyer Park detention basin that we converted last year to (mostly) native meadow.

The blooms of Indian grass got pleasantly in the way of this shot.

With nowhere else to go in a sea of soccer and baseball fields, the monarch kept circling around the planted meadow, encouraging patient waiting for a chance at an unobstructed view. Finally, a clear shot from 100 feet away, while it perched briefly on a river birch. Congratulating myself on some success with a powerful camera, I plunged into the meadow to weed out a small clump of foxtail grass that would become way too numerous if allowed to go to seed.

And there, five feet away from my tugging and clipping, landed the monarch, easily photographed with an iPhone,

with a coppery background of Indian grass. That's what weeding a wild garden does--it immerses the gardener, creating opportunities for serendipity to work its magic.

Just across Snowden Lane from the park, behind Veblen House where our Friends of Herrontown Woods group has fashioned a clearing by removing invasive shrubs and wisteria, another sort of caterpillar munched on the leaves of common milkweed, which has prospered in the resulting sunlight.

Displaying proper Princeton colors, the milkweed tiger moth needed every milkweed plant there, and then some. We came back a week later and found every milkweed stripped down to bare stems. The common milkweed's strategy of aggressive underground spreading becomes more understandable, given the voracious appetites of these caterpillars.

Also called the milkweed tussock moth, the caterpillars become more colorful as they grow. As an adult moth, they are said to retain the cardiac glycosides they pick up from eating milkweed, and warn bats of their unpalatability by emitting a click as they fly about at night.

With summer almost over, a first sighting of a monarch larvae--on a purple milkweed, of which there are very few in Princeton, for some reason. Common milkweed can be a bit too aggressive in a garden, and swamp milkweed disappeared from our garden after a few years. Purple milkweed with its showy blooms may be a good alternative, if we can find any seed after the hungry caterpillar is done.