HR: 08:30h
AN: H51J-03    [Abstracts]
TI: Saturation Overland Flow in Forests? A Model Evaluation
AU: * Rosin, K
EM: rosink@interchange.ubc.ca
AF: University of British Columbia, 2401-2424 Main Mall, Vancouver, BC V6T 1Z4, Canada
AU: Asadian, Y
EM: yeganeh@interchange.ubc.ca
AF: University of British Columbia, 2401-2424 Main Mall, Vancouver, BC V6T 1Z4, Canada
AU: Weiler, M
EM: markus.weiler@ubc.ca
AF: University of British Columbia, 2401-2424 Main Mall, Vancouver, BC V6T 1Z4, Canada
AB: Overland flow generated from saturated areas contributes substantially to storm runoff in many humid watersheds. Several rainfall-runoff models have incorporated saturation excess overland flow (SOF) as an important runoff generation mechanism. This includes our Sensitive Area Mapping Model (SAMM), which has been applied to the entire province of British Columbia (BC, Canada) to predict the effects of changes in forest management practice on hydrology. SAMM, and in particular its SOF module, is evaluated with field studies in forested watersheds with different precipitation regimes throughout BC. To detect saturated areas, five sampling methods were tested and compared: (1) Saturation occurrence samplers were applied; (2) temperature loggers installed to detect delays in soil temperature changes when saturation occurs; (3) SOF controlling morphology characteristics were delineated; (4) wetness indicator plants registered; and (5) soil profiles were analyzed. Our research demonstrates that all five methods can be applied to identify SOF generating areas. The saturation occurrence samplers and temperature loggers provide a good temporal resolution detecting SOF, whereas the other methods are based on long-term averaged characteristics. The assessment of morphology, indicator plants and soil profiles (MIS) can be applied to entire watersheds, whereas the other two methods are limited to smaller areas. Consequently, saturation occurrence samplers and temperature loggers were installed in a research forest to compare the temporal variability of SOF with the predictions of SAMM. Furthermore, the MIS methods were applied to evaluate the spatial variability of SOF in four catchments of different climate (Pacific coast/wet, mainland/moderate, Okanagan/dry, Rocky Mountains/alpine). In each basin more than a hundred forested 25m grid cells were sampled and analyzed. The combination of morphology, indicator plants, and soil profile data allowed estimating several indices which all express each grid cell's disposition to generate SOF. These indices are compared to our model's saturation prediction with rank correlation tests and Kappa statistics. Our research provides valuable information about the relevant processes that control SOF in forested ecosystems with different precipitation regimes. Furthermore, our study presents methods to evaluate SOF modules of hydrologic models. This diagnostic tool helps us to select models which describe the internal characteristics of a watershed appropriately.
DE: 1847 Modeling
DE: 1850 Overland flow
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: 2007 Fall Meeting