Birchbank Drainage Wars: Episode #179 - "The Culvert"

The Cascades at Birchbank

Challenge question: Where does Upper White Hills Brook flow to? That's the scenic brook at Birchbank with the cascades, two bridges, and a random chimney in the forest. 

Sorry, that was a trick question. It doesn't flow to anywhere, but disappears into the sands of Birchbank. Once the brook hits the big flat area at the bottom of the hill, it braids out into various ever-changing channels across the sandy floodplain.  During a typical dry summer, the water will disappear into the ground.  If it's the wet season, the channels will come back together when they hit the railroad embankment, which acts like a dam to keep the brook from reaching the Housatonic River. 

LIDAR image showing brooks, recharge ponds, and RR tracks
(click to enlarge)

(As an aside, people often assume there must also be a matching "Lower White Hills Brook." There is not. This is a brook that flows through an old Huntington district called "Upper White Hills." So the word 'upper' describes the district, not the brook.) 

One of the smaller recharge ponds. 
The water level dropped after ice formed.

Water in the man-made channel along the railroad tracks will make it's way to the first of several man-made groundwater recharge ponds that feed a wellfield operated by the Aquarion Water Company. The wellfield is only used in times of drought, since it's expensive to pump the water out of the ground and up the hill and yonder to Means Brook Reservoir.  The recharge ponds were originally designed for Housatonic River water to be pumped in, but are now filled exclusively with Birchbank runoff.  Aquarion's pipeline goes straight up the precipitous hill at the trailhead parking lot. Pro tip: Don't try to walk up the pipeline, it's steeper than it looks.

That's how the drainage normally works at Birchbank. There are some smaller intermittent waterways that spill down the hillside to feed the recharge ponds, like the little brook near the bench. But every so often, maybe once or a few times a year during the rainy season, we'll have a lot of rain when the recharge ponds are already full and can't take any more water. At that point, the excess water runs south down a man-made channel at the base of the railroad tracks to an old culvert that crosses Indian Well Road and the tracks near the trailhead. It's right where the road crosses the tracks. 

This old culvert channels floodwaters across
Indian Well Road and the tracks

Did the brook always disappear into the sands or was it diverted and captured?  LIDAR images seems to show an old channel going straight to the Housatonic, although it most of the water probably always sunk into the sands because the railroad track were built right across the channel with no bridge or culvert.  The recharge ponds were not built until the 1970s. 

At any rate, that all seemed to be working pretty well. Occasionally the emergency overflow channel would get clogged up with fallen trees at the south end, and then the floodwaters would jump the channel and flow across the Plant Management Area, spreading invasive seeds. A volunteer trails crew recently cut up some of the logs that were blocking the channel. 

And then, during an exceptionally rainy day last week (maybe 4" on top of saturated ground), we were sent the picture below: 

Birchbank Trail. That's not good.
(Photo from Ted)

We had never seen the water that high. In the past, it never even got up to the trail, and now it was a foot or two deep on the trail. A few hours later, the water had receded by about a foot, but was still up to the top of the old stone culvert and swirling into it with great force and (photo below). 

Flood waters going into the culvert

As we suspected, when the flood waters dropped, there were some logs, branches, and leaves clogging up part of the culvert. Once the water level receded to a safe level, the clog was ripped apart, and backed-up water really gushed into the culvert. 

Yup. The culvert is clogged. 
(Photo about 1 week after the flood)

The biggest log was too heavy to drag away. After about ten days, the channel was completely dry and the log could be safely cut up and removed. The surrounding thorny brush was also cut back. It had been catching leaves and sticks and made access to the culvert difficult. Once the work was done, the old stone culvert was revealed. It may date back to the 1800s and is pretty big inside (maybe 5 feet tall?). Take a look. 

All cleared!

This is the same view point as the previous flood photo 

The culvert was cleaned out just in time as it turned out, because heavy rain was forecast for that night. The channel was also cleaned out where flood waters had created dams. The next morning, water was everywhere and once again flooding Indian Well Road at the state park. What would Birchbank look like? 

The culvert. Wow. 

But the trail isn't flooded. It's a normal flood.

It was surprising how much water was flowing through the culvert considering the channel was bone dry the day before. Good thing the log had been cut up and carted away the day before, or it would have been blocking the culvert again. At any rate, we're now aware that we should be checking that culvert routinely or the trail can get flooded.