Hillslope‐derived blocks retard river incision. Issue 10 (27th May 2016)

• Record Type: Journal Article
• Authors: Shobe, Charles M.; Tucker, Gregory E.; Anderson, Robert S.
• Is Part Of: Geophysical research letters. Volume 43:Issue 10(2016)
• Page Start: 5070
• Page End: 5078
• Publication Date: 2016-05-27
• Subjects: fluvial geomorphology -- landscape evolution -- erosion -- bedrock rivers -- hillslope geomorphology -- sediment transport; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2016GL069262
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: 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. Key Points: Large blocks of rock in knickpoints represent a hillslope‐driven negative feedback on river incision A 1‐D model shows that rapid river erosion causes an influx of blocks that inhibit further erosion This autogenic feedback may stall landscape evolution and complicate river profile analysis