The problem of underpowered rivers

Abstract

This study has hypothesized that for many rivers the trade‐off between flow accumulation and the decrease in slope along channel length means that stream power increases downstream and, moreover, that given the low slope angles in headwater and low‐order streams, they would have insufficient stream power to erode let alone transport sediment. The study considered the stream power profile, the particle travel distances and the application of the Hjulström curve based on the velocity profile of nine, large UK catchments. The study showed that: Some rivers never showed a maximum in their longitudinal stream power profile, implying that some rivers never develop a deposition zone before they discharge at the tidal limit. Particle travel distances during a bankfull discharge event showed that for some rivers 91% of the upper main channel would not be cleared of sediment. Furthermore, while some rivers could transport a 2 mm particle their entire length in one bankfull event, for another river it would take 89 such events. The Hjulström curve shows that for three of the study rivers the upper 20 km of the river was not capable of eroding a 2 μm particle. The study has shown that for all rivers studied, erosion is focused downstream and deposition upstream. Many UK rivers have a dead zone where, on time scales of the order of centuries, no erosion or transport occurs and erosion only occurs in the lower courses of the channel where discharge rather than slope dominates – we propose these as underpowered rivers. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

Phosphorus supply and floodplain design govern phosphorus reduction capacity in remediated agricultural streams

“…Closely interlinked with sediment conveyance in channels is the instream transport and storage of P, governed by fluvial processes (deposition/resuspension of sediment-bound P; Ballantine et al, 2009;Noe et al, 2019), redox processes (adsorption/desorption of soluble reactive P [SRP] to SS; Sandström et al, 2021) and geomorphic stability (streambank erosion;Fox et al, 2016). Channel bed sediments can store high amounts of P (Ballantine et al, 2009) and although deposition has been found to dominate in headwater reaches owing to stream power limitation (Worrall et al, 2020), sediment-bound P becomes susceptible to remobilization during high flow events (Bowes et al, 2003). Streambank erosion due to bank failures in agricultural streams can also be a significant source of P export, particularly in P-rich bank soils (Fox et al, 2016;Kronvang et al, 2013;Landemaine et al, 2015), but the efficacy of management strategies to counter this remains underexplored.…”

Rivers Try Harder. Reversed “Differential Erosion” as Geological Control of Flood in the Large Fluvial Systems in Poland

“…The pattern of geological setting, which we reveal in Figures 2-7 and idealized on the scheme in Figure 8, can be adopted as an environmental framework by hydrotechnical engineers who aim to develop instream river training [73,74]. Such a design practice faces a problem of too high stream power [39,[75][76][77][78][79][80][81][82][83][84][85] in the channel which leads to erosion. There are few concepts of energy dissipation of the stream.…”

“…As the bedrock, we regard not only the Mesozoic solid rocks (limestones, sandstones) but also glacial tills and lacustrine (or ice-dammed lake) cohesive sediments (mostly clays) deposited during the Cenozoic, but before the Holocene. These sediments are resistant to erosion (in comparison to the Holocene alluvial sand) due to their cohesive strength [38,39] and due to strength received from glacial pressure-preconsolidation [40][41][42]. The lines of the upper limit of the non-alluvial protrusion were marked by a color that refers to the age according to the chronostratigraphic chart [43].…”