Estimating the thickness of colluvial fill in unchanneled valleys from surface topography

Two procedures for estimating the thickness of colluvium in unchanneled valleys using easily measured surficial characteristics are proposed. Depth-to-bedrock predictions are tested at 12 sites in Northern California and Washington where surface topography is known and the depth of colluvial infilling has been independently determined. The contour displacement is defined as the map distance between the intersection of tangents to side-slope contour segments on opposite sides of an unchanneled valley and the actual position of the contour in the valley axis.--Modified journal abstract.