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Geomorphology » Fluvial Audit
The Fluvial Audit (FA) uses contemporary field survey, historical map and documentary information and scientific literature resources to gain a comprehensive understanding of the river system and its catchment. FA is part of a sequence of survey types that we can offer to address specific issues on the river channel, floodplain and catchment scale.
In the field, the river is divided into a series of reaches defined by natural changes in the geomorphological controls of the river system. In addition to reach-aggregated information on channel dimensions, bank properties, flow types, anthropogenic controls and catchment influences, the specific location, type and severity of bank erosion processes, bank protection works and inchannel modifications are mapped. A photographic record summarises the overall geomorphological character of each reach and provides visual information on specific geomorphological attributes. The field data is either converted into GIS format or entered into a linked ACCESS database.
The standard methodology for FA can be augmented by the addition of field data parameters specific to each projects objectives i.e. bank erosion mechanisms for the River Otter; SAC species habitat requirements (silt deposits, fine cobble bed material etc.) and woody debris dams for the River Usk; and Ranunculion fluitantis and Callitricho-Batrachion vegetation abundance for the River Dee.
Archive data is explored for evidence of past events (Potentially Destabilising Phenomena (PDPs)) within the catchment which may have, or are affecting, the river system by influencing the sediment and water regime, and if so to identify the precise location, timing and impact of the PDP within the river system. Environment Agency archives, discussion with landowners and a review of academic literature identify the location and timing of capital works (flood alleviation schemes), river maintenance (dredging, bank vegetation clearance), and catchment land use changes. Overlays of historic maps explore the location, timing and type of planform change. Information from these sources is entered into a time-chart to facilitate the exploration of links between both the natural and anthropogenic forces (PDPs) and channel change (i.e. planform change, channel aggradation, increased bank erosion).
