The myth of the “stinky mudflats” on a restored Deschutes Estuary (80 percent of the time and healthy)

One of the myths that defenders of Capitol Lake like to mention is the danger of ever present mud flats on a restored Capitol Lake. Obviously, they like to point out, a quiet and peaceful dammed river is much preferable to mud flats. What they don’t mention is the scientific studies that point out how untrue this is.

The recent publication by the Capitol Lake Improvement and Protection Association compared a photo of the current lake with one during the extended drawdown two years ago. That in itself is an inaccurate comparison since that drawdown took the lake to an extremely low water level for an extended period of time. Compared to the twice daily flooding of the estuary, this is a pretty unfair comparison.

From the recent edition of CLIPA’s Capitol Lake Clipper:

Also, from the CLIPA website (under “Know the Facts“):

If we stop dredging the lake and allow this sediment to be dumped into our waterfront the accumulated sediment will: Revert the lake area to stinky mud flats

On the other hand a recent study on how exactly tides would fill the estuary had this to say:

All four restoration alternatives show little to no difference in the amount of submerged or exposed lake bottom. The model predicts that the North Basin, much of the Middle Basin, and the main channel, which would reform quickly after dam removal, would be under water 80% of the time.

If  the estuary were restored, we wouldn’t be trading a beautiful lake for a muddy swamp. Rather, we’re trading a full basin that is polluted and sick for a basin that is full 80 percent of the time and is healthy.

Here is a map that shows to what percentage of time different parts of the current Capitol Lake would be underwater in a restored estuary.

Not exactly the nightmare you’re led to believe.

Here’s a photo from the Washington State Digital Archives (full size version here) showing a typical view of the Capitol Campus in the mid-1930s.

More information: Deschutes Estuary Feasibility Study (Hydrodynamics and Sediment Transport Modeling)