A12. Fluvial Audit

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Fluvial Audit Method Manual (Environment Agency, 2005, p4).

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1. Objectives

  • The Fluvial Audit (FA) uses contemporary field survey, historical map and documentary information to gain a comprehensive understanding of the river system and its catchment
  • This method aims to identify channel conditions at reach-scale, and relate these to catchment-scale conditions (Environment Agency, 2005)

2. Method summary

Figure 1: Flow diagram for a Fluvial Audit (Environment Agency, 2005, p4).

Consultation and desktop assessment are recommended before carrying out Fluvial Audit in the field to ensure accurate understanding of the terrain and catchment issues.

Fluvial Audit assess the channel by dividing the river into a series of reaches defined by natural changes in the geomorphological controls of the river system. These can include drivers such as channel slope, sediment type and flow types. In addition, within each reach, information on channel dimensions, bank properties, flow types, anthropogenic controls and catchment influences, specific location, type and severity of bank erosion processes, bank protection works and in-channel modifications are mapped. This division helps to compare and analyse specific pressures, processes and impacts, and determine priority reaches for further monitoring or investigation.

This method of monitoring encouraged development of further monitoring techniques involving survey and data analysis for morphological assessment such as River Habitat Survey (link to pragmo wiki page).

3. Advantages

  • Allows identification of influence of catchment-scale conditions at reach-scale (e.g. sediment regime, geomorphological processes) to prioritise reaches under the most pressure.
  • Helpful decision support tool (Sear et al., 2003).
  • Better integration of catchment processes in river management.

4. Limitations

  • Time intensive.

5. Costs

Figure 2: data gathered through Fluvail Audit (Environment Agency, 2005, p5)

Trained surveyor and geomorphology specialist.

6. Data analysis

Data gathered in a Fluvial Audit include information on sediment regime, depostion patterns, bank erosion issues, morphological features (pools, riffles, bars) and fluvial processes. This can be mapped using a Geographic Information System (GIS), to demonstrate spatial data and highlight issues. (Sear et al., 2003). Example – Wyre Fluvial Audit, Lancashire - https://www.jbaconsulting.com/knowledge-hub/wyre-fluvial-audit-lancashire/

7. References

  1. Environment Agency & Babtie Brown & Root (2005) ‘Fluvial Audit : A Method for Catchment-Scale Geomorphological Assessment’, Method Description (Report A). Available at: https://www.therrc.co.uk/sites/default/files/files/Designated_Rivers/Axe/fluvial_audit_-_method_description_-_report_a_-_final_a01.pdf
  2. Sear, D. A., Newson. M. D. & Thorne, C. R. (2003) ‘Guidebook of Applied Fluvial Geomorphology’, Defra/Environment Agency Flood and Coastal Defence R&D Programme, R&D Technical Report FD1914
  3. Sear, D. A., Newson, M. D. & Brookes, A. (1995) ‘Sediment-related river maintenance : The role of fluvial geomorphology’, Earth Surface Processes and Landforms, 20(7). Available at : https://onlinelibrary.wiley.com/doi/abs/10.1002/esp.3290200706