Abstract
The analysis of river channel dynamics, and their geomorphological response to environmental change, has frequently focused on channel planform adjustments, often reconstructed using historical maps and aerial photographs. These can provide annual- to centennial-scale records of lateral channel instability at reach, catchment and regional scales. However, regional analyses of vertical
channel instability dynamics (incision and aggradation), although highly desirable, have been far less common and have traditionally been confined to reach scale studies. This study analysed 638 river channel cross sections and associated longitudinal profiles, surveyed on 25 Welsh rivers over the latter half of the twentieth century by various agencies. Net channel bed scour has been the dominant process in 96 % of the rivers studied, with only 4 % of rivers showing no average scour in any period. The maximum recorded scour and fill at individual cross sections were 2.54 m and 2.52 m, respectively whilst average annual rates were in the order of 0.01 m yr-1 and 0.02 m yr-1, respectively. Catchment area and river bed gradient are the most important controls on the
average rate of scour and fill on Welsh rivers, but flow regulation and channelisation are also locally important. The results from this study have important implications for river and flood risk management, because they demonstrate the sensitivity of bed elevation (and consequently channel capacity) to short-term environmental change.
channel instability dynamics (incision and aggradation), although highly desirable, have been far less common and have traditionally been confined to reach scale studies. This study analysed 638 river channel cross sections and associated longitudinal profiles, surveyed on 25 Welsh rivers over the latter half of the twentieth century by various agencies. Net channel bed scour has been the dominant process in 96 % of the rivers studied, with only 4 % of rivers showing no average scour in any period. The maximum recorded scour and fill at individual cross sections were 2.54 m and 2.52 m, respectively whilst average annual rates were in the order of 0.01 m yr-1 and 0.02 m yr-1, respectively. Catchment area and river bed gradient are the most important controls on the
average rate of scour and fill on Welsh rivers, but flow regulation and channelisation are also locally important. The results from this study have important implications for river and flood risk management, because they demonstrate the sensitivity of bed elevation (and consequently channel capacity) to short-term environmental change.
| Original language | English |
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| Publication status | Published - Apr 2011 |
| Event | Advances in River Science Conference - , United Kingdom of Great Britain and Northern Ireland Duration: 01 Apr 2011 → … |
Conference
| Conference | Advances in River Science Conference |
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| Country/Territory | United Kingdom of Great Britain and Northern Ireland |
| Period | 01 Apr 2011 → … |