A12. Geomorphological Dynamics Assessment

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1. Objectives[edit]

  • To gain a detailed understanding process-form interactions at the reach scale.
  • To employ research-level geomorphological methods to provide a comprehensive view of sediment dynamics.
  • To inform long-term solutions to river management problems based on an understanding of geomorphological processes and the identification of causal pressures and links to impacts.

2. Method summary[edit]

The specific GDA methods are tailored to the unique characteristics of each site by an expert geomorphologist so as to ensure that the data collected is relevant to the issues at hand. Research-level methods are often applied from best-practice scientific studies to provide a comprehensive report on the geomorphological dynamics of a site. The methods employed in a GDA assessment should match the spatial and temporal scale at which morphological changes occur, which may involve data collection over multiple years or the study of historic data spanning centuries.

2.1 Principles[edit]

Whilst the methods employed are case specific, they should follow the underlying principles of the method:

  1. The problem should be set within the context of the catchment-scale fluvial system and all its elements (natural processes, morphological change, human activities, catchment plans, stakeholders etc.)
  2. Undertake an intensive data collection programme to identify, measure and monitor cause of the problem and its impact with relation to geomorphological processes.
  3. Use the results to determine the morphological trajectory of the site if no action is taken.
  4. Identify solutions to problem and predict the morphological response to foresee whether it will (a): address the cause and impact of the problem; and (b): not result in adverse morphological changes on-site or elsewhere in the system.

2.2 Outputs[edit]

Use the findings from detailed surveys and data collection to produce a report including:

  1. An assessment of the geomorphological problem, set within the catchment context.
  2. Explanation of the problem, including causes, processes involved, extent and severity.
  3. Identification of the key causes of the problem.
  4. Assessment of the possible solutions and their predicted geomorphological impacts
  5. Propose a sustainable solution which balance to potentially conflicting river management goals.

3. Advantages[edit]

  • Provides a comprehensive understanding of reach-scale processes and dynamics.
  • Uses best practice scientific methods.
  • Is flexible in its use of methods to align with the specific requirements of each case.
  • Assess sites within the context of catchment-scale fluvial processes.
  • Allows for a detailed option appraisal for sustainable solutions to reach-scale problems.

4. Limitations[edit]

  • Requires an experienced geomorphologist to select the right methods and apply them.
  • It is time intensive which often limits the scale of its application.
  • The non-standardised approach to methods means that assessments cannot be compared as easily across space and time.

5. Costs[edit]

Employing an experienced geomorphologist. Potentially multiple years of data collection costs.

6. References[edit]

  1. Environment Agency, 1998, River Geomorphology: A practical guide, National Centre for Risk Analysis and Options Appraisal, Guidance Note 18, Bristol, UK.
  2. Sear, D. A., Newson. M. D. & Thorne, C. R. (2004) ‘Guidebook of Applied Fluvial Geomorphology’, Defra/Environment Agency Flood and Coastal Defence R&D Programme, R&D Technical Report FD1914
  3. Skinner, K., Thorne, C. (2005) Review of Impact Assessment Tools and Post Project Monitoring Guidance. A report by Haycock Associates for SEPA.