Monday, September 6, 2010

A Tale of Two (urban) Seeps

When I think of seeps, I usually think of water dripping down a mossy hillside in the forest.  All it takes to create a seep, though, is a place where water that soaks into the ground is forced out again, usually by bedrock or impervious clay beneath it.  Although they are less common in urban areas, because the presence of pavement and rooftops makes it harder for water to soak into the ground in the first place, they are sometimes found in the city, especially in cities that get a lot of rain and/or snow.

Small Seep

Often when walking from the University of Vermont campus to Centennial Woods I have noticed a wet area on a paved foot trail (see above).  This area of moisture actually creates quite a nuisance in winter, because it freezes and creates ice on the walkway.  I've noticed it many times, but I was surprised to find moisture there even in late summer, which is often the driest time of year.  I looked up the grassy hillside nearby and noticed that there was in fact a wet area, with longer grass and an area of mud and water.

Closeup of Centennial Side Seep

If you look at the first picture, you can see some gravel.  It looks like someone tried to create a small swale for the water from this seep to flow into, but it no longer functions, and the water mostly runs onto the footpath.  There is a lot more flowing water after a rain, but since the area is even wet during this dry period, it seems to be an actual seep (note that it is possible that there could also be some sort of leaky pipe, but I didn't notice any infrastructure of that sort nearby).

I have named this first area 'Centennial Seep' because I see it on the walk to Centennial Woods, and also because it is in the Centennial Brook watershed.

The other seep I've noticed is on the opposite side of the University of Vermont Campus.  I've noticed this seep for a very different reason than the other seep.  Rather than just forming an ice slick, this second seep also includes an area that does not freeze or hold snow as well as nearby areas, especially during the spring and fall.  Shallow seeps tend to contain water at the overall average temperature of the location where they are found, which in Vermont is significantly above freezing.  So, this seep tends to stay liquid until the really cold days of winter come after which time it is covered with a crust of ice.

This seep is not much to look at because it is managed as a maintained lawn:

College Street Seep

However, you can still see some moisture here.  This picture was also taken during a relatively dry time of year:

College Street Seep closeup

It is at the eastern end of College Street, one of the main streets of Burlington.  I have been told that a historic stream channel once followed the approximate route of College street, and since this seep is located at a higher elevation than the highest point on College Street, it probably once was part of the headwaters of this small stream.  I call this seep College Street Seep.

Both of these seeps are in landscaping maintained by the University of Vermont and both also create a hazard to pedestrians due to seepage that freezes during the many months of the year that experience below freezing temperatures in this very cold area.  They also represent wasted opportunity.  If they were fenced off with a nice, small wooden fence and the Centennial seep were slightly re-contoured to keep water off of the footpath, they would soon be home to many wetland plant and animal species.  Planting a few native wetland plants would accelerate this process.  Interpretive signage would also offer an opportunity for people to learn more about wetlands.  I think it would be a great project for someone to take on, though I am not entirely sure who to talk to to get this done.

The location of these two seeps is visible on the maps below.  If you know of other urban seeps in the Burlington area let me know!  I think I know where two more are, and will investigate them at a later time.  I'll also keep an eye on these two, especially when it starts snowing.

View Burlington Urban Seeps in a larger map

1 comment:

  1. I was surprised to find moisture there even in late summer, which is often the driest time of year. I looked up the grassy hillside nearby and noticed....native wetland plants