Understanding how soil thickness and bedrock weathering vary across
ridge and valley topography is needed to constrain the flowpaths of
water and sediment within a landscape. Here, we investigate how soil and
weathered bedrock properties vary across a ridge-valley system in the
Northern California Coast Ranges where topography varies with slope
aspect such that north facing slopes, which are more densely vegetated,
are steeper. In this study, we use seismic refraction surveys to extend
observations made in boreholes and soil pits to the hillslope scale and
identify that while soils are thicker on north facing slopes, the
thickness of weathered bedrock does not vary with slope aspect. We
estimate the porosity of the weathered bedrock and find that it is
several times the annual rainfall, indicating that water storage is not
limited by the available pore space, but rather the amount of
precipitation delivered. Bedding-parallel and bedding-perpendicular
seismic refraction surveys reveal weathering profiles that are thickest
upslope and taper downslope to channels. We do not find a clear linear
scaling relationship between depth to bedrock and hillslope length,
which may be due to local variation in incision rate or bedrock
hydraulic conductivity. Together, these findings, which suggest that the
aspect-independent weathering profile structure is a legacy of past
climate and vegetation conditions and that weathering varies strongly
with hillslope position, have implications for hydrologic processes
across this landscape.