Sunday, April 19, 2009

Glendale Creek

I was in Nashville, checking the news, when I learned of the Whidbey "mudslide" - something related to a failing beaver dam and the community of Glendale. It was easy to find pictures online - a bit harder to actually figure out what happened. This past Monday morning, on the way up to Coupeville to teach a Beach Watchers class, I did some quick reconnaissance.

Water backed up behind Glendale Road, just west of its intersection with Holst Road. It's not unusual for culverts to be too small to deal with high flows on these small creeks, particularly when they jam with mud or debris. Despite attempts to lower water levels with pumps, the road ultimately failed, and much of road fill and all the water headed down the 1 mile of canyon to the beach. Unfortunately, Glendale is built at the mouth of the creek (or more accurately, Glendale is built in the mouth of the creek). The flow coming down the valley was probably too much for the channel through town (rebuilt after the culverts washed out in 1997) and stuff washed down the streeat, into yards and houses, and eventually flowed out over the seawalls at the beach. It sounds like at least folks were warned, so nobody was in the way.

I'm still not quite sure where the beavers fit in. Apparently, they have been busy (as beavers are expected to be) upstream during the last few seasons and had built quite a large reservoir. Was it the failure of this dam that led to the subsequent overtaxing of the Glendale Road culvert? Were the beavers slacking off and not maintaining their dam? Or are the beavers simply convenient culprits? These creeks are subject to periodic gully washers - witness the same watershed (and many other similar ones) on New Years, 1997. And we tend not to leave them enough room. Culverts are sometimes too small. Roads are built in narrow stream valleys, limiting the stream channel's ability to carry large floods. And then, just when the stream wants to spread out at the shoreline, we squeeze it into a narrow ditch so we can build homes on each side. These problems are artifacts of historical development, and they are very difficult to solve, but they are as much a part of the problem as heavy rains and incompetent beavers.

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