Winter Outcome 2015-2016

Dunes are functioning as they should.  Last year, our little area actually gained sand.  It is surprising because the Lake levels are higher than they had been and many other City beaches have been battered and badly eroded.  Look no further than the street-end beaches farther north in Rogers Park or the short stretch between Albion and Columbia for examples.  The dune restoration area was protected more as a function of the direction of the wind and the existence of the pier than anything else.

This year the wind has shifted and we have seen more storms come straight from the east than the northeast.  The northeast winds actually bring us sand and the pier and the plants help stop its movement and hold it in place.  The wind coming from the east does not bring in extra sand from the rest of the beach as nor’easters do, nor is sand caught by the pier.

What you see is that the shoreline is battered by waves and the sand is washed out, at least temporarily, into the Lake.  Where the dune grasses grow, the shoreline is protected.  As you can see in the photos, the grasses have held sand while sand has washed away all around them.  These grasses have roots that may go as far as 15 feet down.  They also spread laterally, or sideways, so that the sand is held by a network of interconnecting roots.  Where the roots don’t exist, the sand washes away.

The grasses can’t withstand everything; they are after all only plants.  Huge, prolonged wave action would eventually damage or destroy them.  They are, however, remarkably tough and can withstand strong storms such as those we have had this past winter, the strongest since Hurricane Sandy.

There are two grasses at play here.  One, the shorter of the two, is called Marram grass or American Sea Grass.  It is so often used to protect shorelines that on Cape Cod there are boardwalks built to go over the grass and huge fines for walking through it.  This grass and the dunes it builds are extremely important for protection against hurricanes there.  It is the same grass used in the erosion control project in Loyola Park, where it also does double-duty as protection from water erosion and not just wind erosion. Here is Marram grass thriving in Loyola Park.

marram erosion control

The second grass, called Sand Reed, has flower stalks as tall as eight feet. It is the grass you see in the following two photos.  It was seeded here about a dozen years ago.  The  photo below is the sand reed approximately ten years ago when the clump was just small.

A&P2299

The next photo is from this winter. The same clump is in the foreground a little to the left this time. Those dozen years have been crucial for developing the root network. Although the grass is dormant for the winter and pretty beat up by wind and waves, the roots continue to do their work.  Next year the grass will be no worse for wear and will grow new leaves and flower stalks with no memory of the storms. You can see that this grass is working to hold the beach in place just as we had envisioned several years ago and will continue to protect the beach, the park and the community for as long as it is there.

erosion 2015 cropped

 

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