Premium
Hillslope‐derived blocks retard river incision
Author(s) -
Shobe Charles M.,
Tucker Gregory E.,
Anderson Robert S.
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl069262
Subject(s) - geology , block (permutation group theory) , fluvial , erosion , sediment , channel (broadcasting) , surface runoff , hydrology (agriculture) , geomorphology , geotechnical engineering , geometry , ecology , mathematics , structural basin , biology , engineering , electrical engineering
The most common detachment‐limited river incision models ignore the effects of sediment on fluvial erosion, yet steep reaches of mountain rivers often host clusters of large (>1 m) blocks. We argue that this distribution of blocks is a manifestation of an autogenic negative feedback in which fast vertical river incision steepens adjacent hillslopes, which deliver blocks to the channel. Blocks inhibit incision by shielding the bed and enhancing form drag. We explore this feedback with a 1‐D channel‐reach model in which block delivery by hillslopes depends on the river incision rate. Results indicate that incision‐dependent block delivery can explain the block distribution in Boulder Creek, Colorado. The proposed negative feedback may significantly slow knickpoint retreat, channel adjustment, and landscape response compared to rates predicted by current theory. The influence of hillslope‐derived blocks may complicate efforts to extract base level histories from river profiles.