Opinion ID: 795489
Heading Depth: 3
Heading Rank: 2

Heading: Potential Sediment Loss from Changes in River Hydraulics and Sediment Transport Rates

Text: 50 The Corps also took a hard look at the second mechanism by which channel deepening could potentially reduce sediment availability in the estuary: changes to river hydraulics and sediment transport rates. Exhibit J to the 2003 FSEIS thoroughly analyzes this dynamic and concludes that channel deepening will have no appreciable impact on sediment transport. The Corps prepared Exhibit J in direct response to concerns from Washington and Oregon in 2000 regarding sediment transport. Thus throughout numerous years of study, the Corps did not simply stake out a position and attempt to defend it; consistent with the dictates of a hard look, the Corps remained open to input from stakeholders and conducted new analyses to address their concerns. See Friends of the Payette v. Horseshoe Bend Hydroelectric Co., 988 F.2d 989, 995 (9th Cir.1993). 51 As a threshold matter, Exhibit J scrupulously considers the cumulative impact of the channel deepening project on sediment availability in conjunction with other projects, including the MCR project, jetties, and the Federal Columbia River Power System. The FSEIS reveals that river flow rate mediated by the Federal Columbia River Power System dams —not any past or future dredging in the navigation channel— is the overwhelming driver of changes to sediment availability in the estuary: The reduction in the Columbia River's net sand discharge to the MCR since the early 1900's is related to lower Columbia River flood discharges and not the navigation channel or the MCR jetties. Regarding the MCR jetties, the FSEIS notes that they have had some impact on sediment availability, by reducing sand movement from the MCR into Baker Bay and across Clatsop Spit into the south channel and by causing a large discharge of sand from the MCR to the ocean. However, Exhibit J repeatedly underscores the reality that [d]eepening will not reduce the available sand supply and the expected hydraulic changes [from channel deepening] are too small to measurably alter sand transport or erosion/ accretion in the river or estuary. Ultimately, deepening the navigation channel in the river and estuary will not alter the sand transport through the MCR nor the sediment budget of the littoral cell. The independent Sustainable Ecosystems Institute expert panel subsequently affirmed the Corps' extensive sedimentation analyses. As a further indication of the comprehensiveness of the Corps' studies, Washington and Oregon withdrew their objections and certified the project upon considering the new analyses. 52