Quantifying the contribution of bank erosion to a suspended sediment budget using boat‐mounted LiDAR and high‐frequency suspended sediment monitoring

• Published in: Earth surface processes and landforms Vol. 48; no. 14; pp. 2920 - 2938
• Main Authors: Haddadchi, Arman, Bind, Jochen, Hoyle, Joanna, Hicks, Murray
• Format: Journal Article
• Language: English
• Published: Bognor Regis Wiley Subscription Services, Inc 01.11.2023
• Subjects: Bank erosion; Channel erosion; Deposition; Environmental monitoring; Environmental restoration; Floodplains; fluvial processes; Lidar; LiDAR surveys; Polls & surveys; remote sensing; river bank erosion; River banks; River beds; River channels; River erosion; River restoration; Riverbanks; Riverbeds; Rivers; Sediment; Sediment load; Sedimentation & deposition; Sediments; Soil erosion; Strategic management; Surveys; Suspended load; suspended sediment; Suspended sediments
• ISSN: 0197-9337; 1096-9837
• DOI: 10.1002/esp.5667

Understanding the physical processes as well as the hydrological and morphological factors that influence channel bank erosion is important for river restoration and the management of the floodplain and associated ecosystems. In this study, we introduced an innovative approach to quantify river bank erosion and its contribution to a reach fine sediment budget by combining repeat bank erosion surveys using a jetboat‐mounted LiDAR scanner with concurrent high‐frequency suspended sediment load measurements into and out of the surveyed reach. Using this information, we established a sediment budget for a 5.5‐km‐long study reach of the lower Ōreti River, Southland, New Zealand. A total of three surveys were conducted along the study reach to understand changes in the bank erosion contribution to suspended sediment load at different time scales. The first two surveys were separated by a short period of 8 weeks, and the third survey followed 2.5 years later. The measured volumes of fine sediment rendered from bank erosion equated to 25% and 29% of the measured outflowing suspended load over these two inter‐survey epochs, respectively. By comparison, the net contribution of measured bank erosion and derived fine sediment deposition on the riverbed to the outflowing suspended load was 12% over the first, shorter epoch and 25% for the second, 2.5‐year epoch. These results highlight the important role of in‐channel sediment deposition in the variability of net suspended sediment exports from channel reaches experiencing bank erosion. The approach used in this study has a unique capability to accurately monitor bank erosion and obtain high‐resolution topography data capturing changes in river banks over different time periods. This study introduces an innovative approach to quantify bank erosion by combining repeat bank erosion surveys using a jetboat‐mounted LiDAR scanner with concurrent high‐frequency suspended sediment load measurements into and out of the surveyed reach. The combined bank erosion and sediment load dataset enabled us to derive the absolute and net contributions of bank erosion to the reach sediment budget and to estimate the impact of flood events on channel bank contributions to catchment suspended sediment yield.