Complex sentence: It is sustained by dredging in Budd Inlet and Capitol Lake, an impoundment of the Deschutes River, which would otherwise recreate its historical estuary with annual of sediment deposit.
Split into simpler sentences: It is sustained by dredging in Budd Inlet and Capitol Lake, an impoundment of the Deschutes River. Without dredging, the Deschutes would recreate its historical estuary with annual of sediment deposit.