Geomorphic river sensitivity: addressing spatio-temporal complexities of a "perfect landscape"
The geomorphic sensitivity of a river is dependent on three key attributes: the mix of imposed and flux controls that govern the erosion-deposition dynamics occurring at any position in a catchment, system preconditioning that results from legacies of historical capacity for adjustment; and catchment scale sediment (dis)connectivity that controls the expression of geomorphic change in a catchment. This thesis uses these three geomorphic attributes to assess the geomorphic sensitivity of rivers across the case study Richmond River catchment, NSW, Australia. It also provides a package of remote sensing techniques and workflows for assessing geomorphic river sensitivity, that others can adapt and use in their own catchments.
In this digital era of publically available catchment wide datasets, access to high computational power and semi-automation, it is now possible to quantify the geomorphic attributes of a landscape and assess trends and patterns with a high level of confidence. In order to quantitatively assess the pattern and gradient of geomorphic river sensitivity across an entire catchment, along with field investigation, this research harnesses the information embedded within Digital Elevation Models and historical planform records. The work on geomorphic controls uses readily available remote sensing datasets to assess the mix of imposed and flux controls operating on different river types along longitudinal profiles. Univariate and bivariate statistics is used to assess relationships between controls, and the envelopes and gradient of controls that explain the variability and pattern of river types in a catchment. The research on historical capacity for adjustment tracks the geomorphic adjustment across the Richmond catchment since European colonisation and provides an approach to categorise the geomorphic sensitivity of rivers across a catchment. A method for assessing whether rivers are geomorphically Fragile, Active Sensitive, Passive Sensitive, Insensitive and Resistant is presented. The research on sediment (dis)connectivity assesses the role of system (de)coupling on network scale sediment flux to identify hostspots of channel adjustment. This thesis integrates this research on geomorphic controls, historical adjustment and sediment connectivity to assess the contemporary and future sensitivity of rivers in the Richmond catchment. In addition to this, technical papers and chapters provide novel GIS workflows for rapidly, semi-automating assessment of geomorphic attributes across a catchment using publically available datasets. Workflows have been built for the semi-automation of valley segment mapping across a catchment, and the semi-automation of quantification of imposed and flux controls across a catchment.