The importance of sediment control for recovery of incised channels

Dairy Arm drains a 39.8 km 2 catchment in the Hunter Valley, Australia, and recently began recovery from post-1949 incision. Recovery involved cessation of upstream progressing incision, leaving a 400-m long upper intact alluvial zone. Post-1985 incision in the 5.5 km incised zone re-exposed buried large wood and eroded bank-side trees, forming log steps which are natural energy dissipators. Degradation in a small section of incised channel bed stranded remnant parts as the contemporary flood plain. Stoloniferous and rhizomatous grass invasion of the developing flood plain accelerated overbank deposition and stabilised river banks. The lower 5 km depositional zone has started to erode over most of its length. In the upper section, pools and riffles formed by degradation, and the bed is now narrower and deeper than at any time since incision started in 1949. A recent decrease in annual rainfall reduced the frequency of flood disturbance, allowing vegetation to survive.