I live near a system of lakes, connected by locks and rivers. A few years ago there was strong rain, and they started to flood. The city usually opens a lock,

I live near a system of lakes, connected by locks and rivers. A few years ago there was strong rain, and they started to flood. The city usually opens a lock, to let a larger lake drain into a smaller lake. Only, there was so much sediment, it clogged up the lock! Now the city needs to spend 10s of millions on dollars to drudge the lakes.