The spatial variability in throughfall and soil moisture in a coastal British Columbia forest

Soil moisture and throughfall measurements in a ~1ha forested watershed and an adjacent clearcut in the Malcolm Knapp Research Forest (BC) showed that average canopy interception was 15% for 53 storms. Interception was relatively greatest for small storms (<20mm). The throughfall distribution became spatially more uniform with increasing rainfall. Soil moisture in the clearcut was consistently higher than in the forest. The soil moisture pattern was persistent and dictated by wet areas in areas of topographic convergence for both catchments. The soil moisture pattern on the hillslope was less persistent than at the catchment scale. The transition from the wet to the dry state occurred quickly in approximately 8 days for both catchments. The larger variation in soil moisture change for small (<20mm) storms and the larger soil moisture change in response to summer storms in the clearcut than the forest highlight the effects of canopy interception on soil moisture.