Integrating channel design and assessment methods based on sediment transport capacity in gravel bed streams

Natural channel design (NCD) and analytical channel design (ACD) are two competing approaches to stable channel design that share fundamental similarities in accounting for sediment transport processes with designs based on hybrid fluvial geomorphology and hydraulic engineering methods. In this paper, we highlight the linkage between ACD's capacity/supply ratio (CSR) and NCD's sediment capacity models (FLOWSED/POWERSED), illustrating how ACD and NCD have reached a point of convergent evolution within the stream restoration toolbox. We modified an existing CSR analytical spreadsheet tool which enabled us to predict relative channel stability using both conventional bed load transport equations and regional sediment regression curves. The stable channel design solutions based on measured data most closely matched the Parker (ACD) and/or Pagosa good/fair (NCD) relationships, which also showed the greatest CSR sensitivity in response to channel alterations. We found that CSR differences among the transport relationships became more extreme the further the design width deviated from the supply reach, suggesting that a stable upstream supply reach may serve as the best design analog. With this paper, we take a step toward resolving lingering controversy in the field of stream restoration, advancing the science and practice by reconciling key differences between ACD and NCD in the context of reach scale morphodynamics.

Automated summary

Natural channel design (NCD) and analytical channel design (ACD) are two competing approaches to stable channel design that both consider sediment transport processes. This paper highlights the connection between ACD's capacity/supply ratio (CSR) and NCD's sediment capacity models (FLOWSED/POWERSED), demonstrating their convergent evolution. By modifying an existing CSR analytical spreadsheet tool, the researchers were able to predict channel stability using conventional bed load transport equations and regional sediment regression curves. The study advances the field of stream restoration by reconciling key differences between ACD and NCD and providing insights into reach scale morphodynamics.