TY  - JOUR
PY  - 2008//
TI  - Integrating uncertainty: Canyon Creek hyperconcentrated flows of November 1989 and 1990
JO  - Landslides
A1  - Jakob, Matthias
A1  - Weatherly, Hamish
SP  - 83
EP  - 95
VL  - 5
IS  - 1
N2  - Canyon Creek drains a 79 km 2 watershed in northwestern Washington State. Extensive logging occurred from the mid-1960s to 1980s, which resulted in numerous slope instabilities and a several order of magnitude increase in sediment supply to the creek. On November 9, 1989, a hyperconcentrated flow with a peak discharge of 450 m 3 /s destroyed one house on the fan. A forensic investigation of the event suggests that a temporary landslide dam may have formed at two coalescing earthflows about 4 km above the fan apex. The 1989 hyperconcentrated flow caused significant aggradation on the fan. One year later to the day, a significant flood occurred, which ran over the aggraded fan surface from the 1989 event. This latter event destroyed four more homes mostly through bank erosion and rendered a section of county road impassable. FLDWAV, a flood routing model capable of simulating unsteady flow conditions, was used to model landslide dam breaches for a number of different dam heights at the earthflows. Modeling results were then combined with historic air photograph interpretation, dendrochronology, and eyewitness accounts to construct a frequency-magnitude relationship for hyperconcentrated flows at Canyon Creek. FLDWAV results were combined with a hyperconcentrated flow runout model (FLO-2D) on the fan to estimate maximum flow depth and flow velocity for the design event, a 500-year return period with a predicted peak discharge of 710 m 3 /s. A large range of mitigation measures were reviewed, but it was concluded that buy-outs would be the most effective risk reduction measure. Property acquisition commenced in 2004.<p /> 
LA  - 
SN  - 1612-510X
UR  - http://dx.doi.org/10.1007/s10346-007-0106-z
ID  - ref1
ER  -