Premium
Channel bed evolution and sediment transport under declining sand inputs
Author(s) -
Gran Karen B.,
Montgomery David R.,
Sutherland Diane G.
Publication year - 2006
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2005wr004306
Subject(s) - sediment transport , flume , geology , bedform , sediment , grain size , channel (broadcasting) , bed load , pyroclastic rock , geomorphology , hydrology (agriculture) , river morphology , geotechnical engineering , flow (mathematics) , geochemistry , volcano , geometry , mathematics , engineering , electrical engineering
Coupled field and laboratory investigations explore links between bed surface structure development and sediment transport as sand inputs decline. On the Pasig‐Potrero River, we investigated channel recovery following emplacement of sand‐rich pyroclastic deposits in the 1991 eruption of Mount Pinatubo, Philippines. As sediment inputs declined from 1996 to 2003, surface grain size increased, clast structures formed, and sediment mobility and bed load transport rates declined. Our field results parallel those from flume experiments studying highly energetic channels with similar sand contents. As the feed mixture shifted from 70% to 40% sand, surface grain size and gravel interactions increased, forming clusters and armor patches. Bed reorganization into patches initially accommodated coarsening with minimal effect on bed load transport rates, roughness, or friction angle within sandy transport zones. As sand declined further, gravel jams interrupted the connectivity of sandy transport zones, lowering transport rates. Patch development lowered the threshold for the transition from sand‐dominated to gravel‐dominated transport, focusing this transition over a narrow range of sand content.