Designing forward with an eye to the past: Morphogenesis of the lower Yuba River

Abstract

The early geomorphic evolution of the lower Yuba River (LYR), northern California, up to 1906 is reconstructed using cartographic, documentary, topographic, and stratigraphic evidence. The importance of early river mining is identified along with rates and patterns of floodplain aggradation and channel incision at the turn of the 20th century. The LYR is a classic example of anthropogeomorphic transformation of a river by episodic hydraulic mining sedimentation. This was followed by channelization, damming, dredging, and other engineering works to redirect, contain, and stabilize channels. These geomorphic changes and engineering controls continue to govern channel and floodplain form and process, control the trajectory of river responses, and constrain flood control, water quality, and aquatic ecosystem management options. Returning a river system to a prior condition should not be the primary goal of river rehabilitation projects, especially if hydrologic inputs have substantially changed. Reconstructing former conditions may be impractical and unsustainable under modern circumstances. Instead, fluvial systems should be designed and managed for present inputs and processes while anticipating future conditions. Rapid changes in land use and climate that generate changes in runoff and sediment loadings are likely to generate morphological instability, and these changes should be considered in the design and management of fluvial systems. The past geomorphic evolution of fluvial systems should also be considered in design and management decisions to recognize trajectories and suppressed tendencies. Recognition of trends and system vulnerabilities may avoid potential blunders, such as removing critical stabilizing works. Complex causalities may be difficult to reconstruct from geomorphic form alone, however, due to process-form dynamics. Detailed research on the geomorphic and engineering history of a river is essential, therefore, if substantial changes and morphologic instabilities have occurred.

Geomorphic Evolution of a Gravel‐Bed River Under Sediment‐Starved Versus Sediment‐Rich Conditions: River Response to the World's Largest Dam Removal

“…Unlike some sediment pulses that originate from broad land use changes (Gran & Czuba, ; Madej & Ozaki, ), the Elwha River sediment pulse did not appear to be affected substantially by long‐term sediment storage within the watershed (i.e., storage along the middle and lower reaches). Gran and Czuba () determined that network structure can affect sediment‐pulse dispersion substantially, especially if hillslopes shed new sediment down multiple tributaries with similar timing and sediment becomes stored within the valley over the long term (e.g., James, ; Lisle et al, ; Wohl, ). In such cases a sediment pulse originates with different mechanisms than that of mainstem dam removals, which effectively function as point sources.…”

“…Although many studies have examined the evolution of fluvial sediment pulses (or "slugs," or "waves") and their associated geomorphic effects Gran & Czuba, 2017;Humphries et al, 2012;Lisle et al, 2001Lisle et al, , 1997Madej & Ozaki, 1996;P. A. Nelson et al, 2015;Nicholas et al, 1995;Podolak & Wilcock, 2013), opportunities to study these processes before, during, and after such an event at field scale are rare because most large sediment pulses are unanticipated (e.g., Gran & Montgomery, 2005;Guthrie et al, 2012;Major et al, 2000), and many that were foreseeable began before the era of quantitative geomorphology (Ferguson et al, 2015;James, 2015;Knighton, 1989;Kondolf et al, 2002;A. D. Nelson & Church, 2012).…”

“…The response of fluvial channels to a sediment‐supply disturbance is one of the longest‐standing problems in geomorphic process studies (e.g., Gilbert, ) and is critically important to understanding anthropogenic influences on watersheds (Nilsson et al, ; Syvitski et al, ; Wohl, ; X. K. Yang & Lu, ) as well as to predicting river response to natural disasters (Anderson et al, ; Pierson & Major, ). Although many studies have examined the evolution of fluvial sediment pulses (or “slugs,” or “waves”) and their associated geomorphic effects (Cui, Parker, Lisle, et al, ; Cui, Parker, Pizzuto, et al, ; Gran & Czuba, ; Humphries et al, ; Lisle et al, , ; Madej & Ozaki, ; P. A. Nelson et al, ; Nicholas et al, ; Podolak & Wilcock, ), opportunities to study these processes before, during, and after such an event at field scale are rare because most large sediment pulses are unanticipated (e.g., Gran & Montgomery, ; Guthrie et al, ; Major et al, ), and many that were foreseeable began before the era of quantitative geomorphology (Ferguson et al, ; James, ; Knighton, ; Kondolf et al, ; A. D. Nelson & Church, ). An intentional dam removal and associated release of impounded sediment provides an uncommon opportunity to quantify in detail the response of a fluvial landscape to an abrupt, large‐scale increase in sediment supply.…”

Detailed assessment of spatial and temporal variations in river channel changes and meander evolution as a preliminary work for effective floodplain management. The example of Sajó River, Hungary

“…next 30-50 years). There is still a demand for detailed geomorphological inputs for management strategies; however, many policy-makers argue with a necessary preservation of the previous channel development trajectories (Thorne et al, 1998;DeVries and Aldrich 2015;James 2015). The next step for managers would be to decide which strategy to adopt: protecting the floodplain (Piégay 1998;Morandi et al, 2014;Alber and Piégay 2017) or defining an erodible corridor where lateral shifting will not be hindered (Piégay et al, 2005;Habersack and Piégay 2007)?…”

Hydrogeomorphic Scaling and Ecohydraulics for Designing Rescaled Channel and Floodplain Geometry in Regulated Gravel–Cobble Bed Rivers for Pacific Salmon Habitat

“…Returning rivers to prior or historical conditions is not a feasible alternative when hydrologic inputs and river corridor extents have been significantly modified. Rather, fluvial systems should be designed for present inputs while factoring in anticipated future conditions related to climate change or management [32]. A fundamental concept for rehabilitating river corridors below dams for salmon is that a rescaled version of the river corridor synchronized to the regulated flow regime can restore habitat quantity and quality [1].…”