The signature of an extreme erosion event on suspended sediment loads: Motueka River catchment, South Island, New Zealand.

摘要: Five years of continuously monitoring turbidity and suspended sediment (SS) at four sites in the Motueka River catchment, northern South Island, New Zealand, has characterised downstream temporal dispersion high SS inputs from an extreme rainfall event. The rainstorm, of>50 year recurrence interval, was concentrated upper Motupiko tributaries delivered outputs re-activated gully complexes landslides. These only appear to activate when a threshold is exceeded. Monitoring stations these captured ∼20- 30-fold increase concentrations event yields, whereas station coast recorded 2- 5-fold increase. yields decayed exponentially back towards normal levels over -2-3 both upstream sites. Field observations suggest that this erosion recovery trend relates more exhaustion/stabilisation transient riparian storage than healing primary by surface-armouring and/or re-vegetation. decay dilution (from other carrying lower concentrations) processes. Similar space-time patterns have been observed Zealand catchments implications for reliability yield estimates based on short records. A method suggested incorporating such events into long-term average yield.