Hillslope and channel evolution in a marine terraced landscape, Santa Cruz, California

A flight of marine terraces along the central California coastline provides a unique setting for the study of topographic evolution. Wavecut platforms manfled by 2-6 m of marine terrace cover deposits are separated by10-50 m tall decaying sea cliffs. Palcocliff edges become more rounded with age, yet the details of the profries and frequent bedrock exposure on the upper slopes imply weatheringlimited Wansport. Five bedrock sueam channels etched through t e marine terrace sequence display one to three distintt convexities n their longitudinal profiles. Detailed hand level surveys ofthe hillslopes and of the stream channel longitudinal profiles constrain hillslope volution and channel incision components of a numerical model of landscape evolution. We account for regolith production as a function of regolith depth. In accord with the field observation that hillslope processes are presently dominated by the activities of burrowing rodents, the transport process i taken to be diffusive. Stream incision is asstuned to bc controlled by stream power, for which we use the surrogate of local drainage area-slope product. Best fits of the numerical model to field data imply: hillslope diffusivity is 10 m 2 kyr•; regolith production rate on bare bedrock is 0.3 m kyr •, and falls off rapidly with regolith cover, and the constant controlling the efficiency of stream incision is 5 to 7 x 10 -7 m '• kyr •.