Changes in lowland floodplain sedimentation processes: pre-disturbance to post-rehabilitation, Cosumnes River, CA

摘要: During the late Holocene, sediment deposition on lowland Cosumnes River floodplain, CA has depended factors that varied temporally and spatially, such as basin subsidence, sea level rise, flow, supply from both Sacramento system itself, anthropogenic changes. Through field investigations analyses of historical maps, bridge core logs, size distributions, we link hydrogeomorphic processes to three stages floodplain sedimentation River. Stage I (1000–200 YBP) combined Holocene pre-disturbance flood overflow anastomosing river deposited spatially variable consisting gray–blue clay (87% clay) interlayered with relatively thin coarser sediment. Pre-disturbance rates up f3.0 mm/year kept pace rise tectonic subsidence. II (200 f10 disturbances caused a rapid increase in 25 between 1849 f1920, reddish-brown sandy (f40% layer overlies deposits. Between f1920 1990 AD, was greatly limited lower because levees inhibited connectivity systems floodplain. this stage, density channel segments decreased by 30% agricultural activities filled secondary channels leveled topography. III (f10 YBP present), post-rehabilitation sand splay complex after 1998 AD resulted intentionally breaching promote habitat at Preserve. The is dominated medium very coarse finer intervening layers. older deposits generally upward coarsening sequence reflects depositional land use changes continue affect D 2003 Elsevier Science B.V. All rights reserved.