Here in NY the State folks made a surprising discovery. Channeling a stream is the worst sort of flood control. Channels allow flood water to pick up speed and when it runs into debris or a turn it will do a lot more flooding and damage. It seems counter intuitive!!
Allowing trees, bushes and water plants to grow on streams and putting in rip-rap on rivers actually reduces flood damage. That lesson was learned when Hurricane Sandy went through the Catskill Mountains a few years ago. NY State has had classes for contractors, to teach them how to repair flood damage without "channeling" streams. Adios Philip43