Bank erosion of an incised upland channel by subaerial processes: Tasmania, Australia

Abstract

The headwaters of many rivers are characterized by gullies and incised streams that generate significant volumes of sediment and degrade downstream water quality. These systems are characterized by harsh climates, ephemeral flows that do not reach bank top, and bare cohesive banks of clay and weathered bedrock. We investigated the rates and processes of bank erosion in an incised canal that has such characteristics. Detailed measurements of bank position were made over two years with a purpose‐built groundprofiler and photo‐electronic erosion pins (PEEPs). Stage height and turbidity were also monitored. The bare banks eroded at 13 ± 2 mm a−1. Erosion is controlled by subaerial processes that loosen bank material. Observations show that needle‐ice growth is important in winter and desiccation of clays predominates in summer. Flows are unable to erode firm cohesive clays from the banks, and erosion is generally limited by the availability of loosened material. This produces strong hysteresis in turbidity during events. Peak turbidity is related to the number of days with low flow between events, and not peak stage. Rehabilitation with a moderate cover of grass is able to prevent bank erosion by limiting the subaerial erosion processes. Projections of current erosion suggest that without vegetation cover the banks are unlikely to stabilize for many years. Copyright © 2000 John Wiley & Sons, Ltd.

Riparian land-use impacts on bank erosion and deposition of an incised stream in north-central Iowa, USA

“…This was done to compare the PEEP data with the streamflow data that had a coarser temporal scale (daily). The PEEPs have been used extensively in various fluvial systems with good results especially for stream bank erosion (Bull, 1997;Couperthwaite et al, 1998;Lawler et al, 1997;Mitchell et al, 2003;Prosser et al, 2000). To our knowledge this was the first study that had so many PEEPs placed on different land-uses and on different bank positions.…”

The importance of high-resolution monitoring in erosion and deposition dynamics studies: examples from estuarine and fluvial systems

“…Indeed, high-resolution approaches with PEEP systems are now being applied by several research teams to different geomorphological and hydrological problems across the world, including beaches, tidal systems, drainage ditches and artificial channels, and snow ablation and accumulation studies (e.g. Mitchell et al, 1999;Stott, 1999;Prosser et al, 2000). However, substantial scope exists for applications to gully, arroyo, dune and hillslope erosion systems too.…”

“…PEEP-3 applications from fluvial, canal, estuarine and nival environments are now available (e.g. Stott, 1999;Mitchell et al, 1999;Prosser et al, 2000). The main design improvements were as follows: (a) sensors were lengthened to 660 mm, and the active length to 200 mm, to allow for higher erosion rates; (b) a second reference cell was added to permit inverted deployment, and to provide confirmation of minimum erosion magnitudes for large events (Fig.…”

“…Many weathering (preconditioning) and detachment (removal) processes are likely to operate at a given site, each varying in relative dominance at different time scales. Antecedent processes also mean that erodibility of the surface material at the time of the key driving event itself changes over time, for example through rainfall and matric suction effects (Simon et al, 2000) or freezethaw action (Prosser et al, 2000). This can induce several different and complex responses to the same destabilizing force, especially for cohesive materials (e.g.…”

The characteristics of gully erosion over rolling hilly black soil areas of Northeast China

“…Moreover, when water becomes ice, its volume would increase 9% more than that of water (Li and Li, 2000). The expansion of water on freezing causes a reduction of granular interlocking within the soil (Dietrich and Gallinatti, 1991), and the migration of unfrozen water towards the freezing front creates further disturbance, sometimes associated with the development of needle ice (Meentemeyer and Zippin, 1981;Prosser et al, 2000). Needle ice generation has effect on the migration of sediment.…”