The Effects of Bank Erosion on Salmon Spawning Habitat in an Upland Gravel-Bed River

Smart, David William Johnston (1996) The Effects of Bank Erosion on Salmon Spawning Habitat in an Upland Gravel-Bed River. MSc(R) thesis, University of Glasgow.

Abstract

Two main problems of channel widening and fine sediment infiltration were identified as major causes of the degradation of salmon spawning gravels in upland rivers in Scotland. They are both commonly attributed to the process of bank erosion. The supply of fine sediment for infiltration into gravel beds is considered by many to be controlled by rates of bank erosion. This study attempts to identify the effects of bank erosion on the condition of gravel-beds and to evaluate its contribution to the fine sediment load of the river. It is also aimed at evaluating the effectiveness of bank protection in reducing fine sediment infiltration. This was done by recording rates of fine sediment infiltration into gravel-beds at various locations through a reach of the river. The redistribution of bank eroded sediment was monitored by tagging fine bank sediment with fluorescent paint and tracing its removal from the bank and its dispersal and deposition both across the channel cross-section and in the downstream direction. Image analysis techniques were developed using computer software that allows quantitative analysis of sediment sample composition to establish likely source areas for the material. Also the morphological and hydraulic conditions were monitored in a reach of the river before and after the bank protection installation to record process changes that may affect sedimentation rates. It was found that there are several physical factors which control the infiltration of fines into gravel-beds. The interaction of these dictates a complex pattern of sediment infilling and matrix development. But infiltration rates were shown to be largely dominated by sediment supply, both within and outwith the channel, although the actual process of infiltration is conditioned by the flow regime and the frequency and magnitude of floods, irrespective of the availability of fine sediment. Bank eroded sediment was found to have a considerable influence on levels of infilling, both locally and further downstream. Finally, although bank protection works have prevented further channel widening it has shown that reducing gravel-bed infilling cannot be achieved isolated stretches of bank protection alone.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Additional Information: Adviser: Trevor Hoey
• Keywords: Ecology
• Date of Award: 1996
• Depositing User: Enlighten Team
• Unique ID: glathesis:1996-74734
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 27 Sep 2019 16:45
• Last Modified: 27 Sep 2019 16:45
• URI: https://theses.gla.ac.uk/id/eprint/74734