Relationships between vegetation and hydrogeomorphic characteristics of British riverine environments : a remotely sensed perspective

Riverine environments are a major linear feature in the British landscape. This thesis examines the short-term relationships between their vegetation (vascular plants only) and hydrogeomorphic characteristics (landforms and processes including episodes of inundation, erosion and deposition). These characteristics constitute the `fabric' of these areas and interact with one another to shape the environment, provide habitats for organisms, control the processes operating, and also affect the movement of energy and matter (sediment, nutrients, debris, organisms) within the riverine system and across its boundaries. The research was designed to explore how remotely sensed data might by used to identify these characteristics. Ground-based and remotely sensed data were acquired for two sites, one on the River Exe (preliminary study) and the other on the River Teme. Remotely sensed data included digital multispectral airborne imagery (Daedalus AADS 1268 ATM) and panchromatic aerial photographs for both sites, and also satellite imagery (SPOT-1) for the River Teme. Relationships between vegetation communities and hydrogeomorphic surface type including valley-side slopes, floodplain, riparian and bar surfaces have been established. These surfaces have a process significance, in terms of episodes of inundation, erosion, and deposition, which has been deduced on the River Exe, and quantified on the River Teme through the use of flow duration and flood frequency indices. Intra-surface variation has also been identified on the bar and reparian surfaces with species being differentiated according to their habitat affinities (wet fringe, damp, river bank and disturbed) and also life strategies eg. ruderal species (Grime et al., 1988). This allowed the development of a rationale for using the vegetation communities and habitat affinities as an indicator of hydrogeomorphic processes, enabling the discharge characteristics of sites with a lack of continuous streamflow data to be crudely and rapidly estimated. A process-based division of the riverscape into areas exhibiting homogeneous vegetation and hydrogeomorphic attributes which may be utilised as a basis for river management strategies is also suggested.