Alluvial landscape evolution in response to deglaciation. A case study from the Thompson River, south-central British Columbia.
Lead Research Organisation:
University of Oxford
Department Name: Geography - SoGE
Abstract
EPSRC : Samuel Woor : EP/L016036/1
The amount of water (discharge) and sediment entering a river control the nature of its flow. Discharge may vary due to hydro-climatic changes, transmitted to river systems either directly via changes in rainfall amounts and intensities, or indirectly via changes in the size of glaciers or factors influencing runoff like vegetation cover. The amount of sediment entering a river may vary due to environmental responses to climatic change, such as increasing or decreasing vegetation. Due to this sensitivity to changing environmental conditions, river systems and the sediments stored within them can act as significant records of past environmental and climatic change over long periods of time (tens of thousands of years in many cases).
Globally, landscapes are already undergoing significant changes as a result of climate change, such as changes in precipitation, vegetation cover, or the disappearance of glaciers. Such changes are likely to result in changes to discharge and sediment inputs into river systems, posing numerous risks to society and industry within their catchments. Mid-latitude regions undergoing rapid glacial retreat, like western Canada, are likely to be especially vulnerable to climate change with resulting down-system flooding, soil erosion and changes in channel morphology. Recent river flooding has highlighted the risks posed to British Columbia specifically, with the extreme flooding events of November 2021 being estimated as the most expensive disaster in the region's history. As such, understanding how river systems adjust to changes in their fundamental controls is increasingly important and requires more studies of their long-term variability.
Models can also be used to help answer these questions. They mathematically relate amounts of sediment and water input to expected changes in the morphometric properties of rivers, such as the steepness of channels, which is useful for predicting future change given changes in these driving factors. However, a lack of field studies of long term changes in river systems from different environmental contexts limits the extent to which the general relationships expected by numerical models can be widely applied. The Thompson River, south-central British Columbia, provides an excellent opportunity to develop a long-term record of river evolution in response to changing discharge and sediment fluxes which can be quantitatively reconstructed. This is because the area has experienced significant climatic and environmental change over the last c.15,000 years following the retreat of ice sheets at the end of the last Ice Age. This project will use a variety of field and laboratory methods to first date the age of sediments sampled from the Thompson River and then estimate past discharge and sediment flux amounts as well as past river morphometry. Relationships between these data will then be compared to recent numerical modelling studies to test their applicability to the Thompson River and evaluate how continued climatic change may influence the landscape into the future. It will also provide new data on the age and long-term evolution of the landscapes of British Columbia, a region for which there are very few studies of past environmental changes, with potential wider relevance to historical and archaeological understandings of the region.
The amount of water (discharge) and sediment entering a river control the nature of its flow. Discharge may vary due to hydro-climatic changes, transmitted to river systems either directly via changes in rainfall amounts and intensities, or indirectly via changes in the size of glaciers or factors influencing runoff like vegetation cover. The amount of sediment entering a river may vary due to environmental responses to climatic change, such as increasing or decreasing vegetation. Due to this sensitivity to changing environmental conditions, river systems and the sediments stored within them can act as significant records of past environmental and climatic change over long periods of time (tens of thousands of years in many cases).
Globally, landscapes are already undergoing significant changes as a result of climate change, such as changes in precipitation, vegetation cover, or the disappearance of glaciers. Such changes are likely to result in changes to discharge and sediment inputs into river systems, posing numerous risks to society and industry within their catchments. Mid-latitude regions undergoing rapid glacial retreat, like western Canada, are likely to be especially vulnerable to climate change with resulting down-system flooding, soil erosion and changes in channel morphology. Recent river flooding has highlighted the risks posed to British Columbia specifically, with the extreme flooding events of November 2021 being estimated as the most expensive disaster in the region's history. As such, understanding how river systems adjust to changes in their fundamental controls is increasingly important and requires more studies of their long-term variability.
Models can also be used to help answer these questions. They mathematically relate amounts of sediment and water input to expected changes in the morphometric properties of rivers, such as the steepness of channels, which is useful for predicting future change given changes in these driving factors. However, a lack of field studies of long term changes in river systems from different environmental contexts limits the extent to which the general relationships expected by numerical models can be widely applied. The Thompson River, south-central British Columbia, provides an excellent opportunity to develop a long-term record of river evolution in response to changing discharge and sediment fluxes which can be quantitatively reconstructed. This is because the area has experienced significant climatic and environmental change over the last c.15,000 years following the retreat of ice sheets at the end of the last Ice Age. This project will use a variety of field and laboratory methods to first date the age of sediments sampled from the Thompson River and then estimate past discharge and sediment flux amounts as well as past river morphometry. Relationships between these data will then be compared to recent numerical modelling studies to test their applicability to the Thompson River and evaluate how continued climatic change may influence the landscape into the future. It will also provide new data on the age and long-term evolution of the landscapes of British Columbia, a region for which there are very few studies of past environmental changes, with potential wider relevance to historical and archaeological understandings of the region.
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