It has been a burden on my heart, these last few months, to see the dismal amount of erosion taking place around May Fete Island. You may know it by a different name, but all alums of Carleton will quickly know which of the two islands in the lower Lyman Lake I’m referring to; and you’ll also know what I mean by erosion.
Any owner of midwestern lake property is only too familiar with the effects of wind, ice, wave action, and other insults upon lake properties. Lyman Lakes, a jewel in the Carleton campus, is no exception. Despite a major rehab project in 1999-2000, shown in this poster now standing at the site, (click to enlarge)———–
erosion of the banks of the two islands continued. The intent and the technologies were not to blame; they were the best known at the time. The problem seems to have been that after biologs were put in place and reseeding was done, ———– the reseeding was done in turf grass, whose roots go only two inches deep or so. And so it was not a great surprise, as time went on, that bank erosion continued at the rate of about one foot per year. Consequently the two islands have lost 16-20 feet in diameter over the years since the year 2000.
If you’ve been near the Lyman Lakes this past week, you’ve noticed that the lakes have been drained and that restoration of the eroded shorelines is in progress. The main contractors involved are from Inver Grove Heights, and I was impressed with their technology and understanding of what’s at stake. The process, as I understand it, is to 1) drain the two lakes down to a level which permits the restoration to proceed. This is done, and reveals a remarkable number of large fish and shore birds we don’t usually see when the lakes are full. It also reveals some astonishing garbage, as shown here.
2) Create new biologs around the perimeter of the islands. These are synthesized from polymer tubes, about one foot in diameter, into which a mixture of compost and sand are blown by large trucks which you see here.
3) Just one row of these biologs around the islands would be puny. So several courses of biologs are being planned, to create a new wall at least four feet high, to hold the soil and plantings which will go into the desolated, slanting perimeter of the islands.
4) What will these plantings be? Well, certainly not the turf grass again. Instead, prairie flora, similar to that seen in many other areas of the campus and arboretum, will be used; their roots often go down several feet, and it’s hoped this will offer a great deal more stability to the landscape than the previous plan. It certainly sounds good to me; how about you? Ed
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