SUPERSLUG: Deconstructing sediment superslugs as a legacy of extreme flows

Project Description

This proposal pushes the frontiers of scientific knowledge by using technical innovation to reveal new and exciting insights into sediment transport legacies of catastrophic geomorphological disturbances in mountain landscapes, such as landslides, rock-ice avalanches, outburst floods, and debris flows and debris floods(ref). These events entrain, mobilise and deposit vast quantities of sediment, and can collectively be described as ‘sediment-rich flows’ (SRF)(refs). SRFs have caused tens of thousands of deaths globally (e.g. ref), destroy or damage important assets such as hydro-electric power (HEP)(ref), degrade water quality and ecosystems(ref), and produce significant secondary hazards along populated river corridors(ref). Globally, vulnerable communities and assets are at risk from immediate geohazard impacts but also from so-called legacy impacts which are commonly overlooked and unquantified and may have greater spatial and temporal reach than the initial SRF.

Enhanced transport of coarse sediment including so-called ‘superslugs’ (or ‘waves’, ‘pulses’) drives rapid river channel modification (e.g. by modifying channel bed elevation, in turn increasing flood hazard)(ref), impacting infrastructure (by scouring bridge footings, blocking HEP intakes and reducing reservoir capacity)(ref) and fluvial ecology (by reorganising channel substrate)(ref). As superslugs translate and/or disperse in fluvial systems they cause elevated suspended sediment loads and plumes which are both in- and out of phase with normal suspended load seasonality; enhanced fine sediment loads are a major disruptor of water quality (as a vector of nutrients and contaminants), impacting human health, exacerbate reservoir siltation and cause damage to HEP turbines, thereby reducing water and energy security and disrupting the operation of water treatment plants hundreds of kilometres from a flood source(ref). The latter are a vital socioeconomic asset in regions that experience increasingly unstable hydrological regimes.