DKARST: modeling abrasional wear of scalloped bedrock in caves (note: this is developmental research grade software that has not been subject to review)

Rachel Bosch and Dylan Ward

Abstract

The extent to which chemical and mechanical erosion each contribute to the erosion of cave passages in limestone is an open question. In cave riverbeds in which the limestone bedrock is partially exposed and partially alluviated, we sometimes see clearly scalloped bedrock. The uniquely soluble properties of limestone imply that these scallops are the result of chemical dissolution. However, because we see silt, sand, and gravel, and because when we visit the same reach of the cave river many times, we see those sediment deposits shift in size and location, we infer that there may also be physical abrasion from sediment impacts on the scalloped bedrock surface. Using our numerical model, DKARST (Does karst abrasion result in scalloped tunnels?), in conjunction with data from previously published dissolution studies, we tested the hypothesis that there are three conditions concerning the balance of mechanical and chemical erosion in karstic limestone: 1) dissolution dominates, 2) dissolution and abrasional contribute at similar rates, and 3) abrasion dominates. This hypothesis was supported by our study, with the addition of a fourth category which allows for the possibility of the bed being armored by sediment deposits, and the surprising result that the area of the phase space in which dissolution dominates far exceeds that in which abrasion would equal or exceed dissolution. Our investigation into the role of mechanical erosion in relation to the scalloping of bedrock in caves provides insight into the relative roles played by mechanical and chemical processes in broader scale landscape evolution, particularly in karst regions dominated by carbonate bedrock.

How does DKARST work?