The dam creating Capitol Lake was not built for the purpose of urban flood control. In fact, the dam actually caused flooding until its managers learned how to mitigate the problems it caused during storms.
The first time the Deschutes River flooded Olympia was the winter of 1951, when a power failure and inexperienced management of the brand new dam forced storm water that normally flowed into Budd Inlet to back up and overflow into nearby streets.
Before that, downtown businesses complained only of inadequate storm sewers, not flooding from the river even at high tides.
A headline in the 1910 Olympia Daily Recorder bragged, “Olympia’s Security from Floods A Big Publicity Boost.”
If anybody wants to ask state taxpayers to foot the bill for perpetual dredging of Capitol Lake, they need to find a better excuse than flood protection.