Sunday, April 19, 2009

Nisqually Delta

The Nisqually Delta might have become a deep-water industrial port had it not been for a groundswell of environmental concern in the 1970s. But the lack of industry does not mean that the delta is okay. Deltas are about rivers spreading their sediment across a broad landscape and about the formation of a complex estuarine system. But then we dike them to create pasture for our cows and to prevent flooding of our valuable farmland (valuable because of the past flooding and the sediments it brought). And then hunters and birders discovered the joys of freshwater waterfowl - and easy access to the wetlands along the tops of the dikes.

At Nisqually, the dikes will be removed soon and tidal processes restored to 750 acres of wetland that still retain some of the 19th century tidal channels. Removal of the dikes means loss of the loop trail - although new paths will still allow access to the restored delta. New dikes will maintain some freshwater areas -- and protect the Refuge headquarters from rising sea level? (I put some additional pictures at

One of the interesting questions that came up recently was the history or purpose of the bench that lies along the saltwater side of much of the main dike - is this an earlier dike or a feature built to allow construction of the dike or a protective berm to protect the main dike from erosion? It represents lots of work, and lots of dirt, and will need to be removed in addition to the main dike to assure that natural drainage is restored to the delta.

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