A12. Geomorphological mapping

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Figure 1: Example of a Geomorphological Map (Seijmonsbergen & de Graaff, 2006)

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1. Applicability and Purpose[edit]

Geomorphological mapping can be used for several purposes:

  • To spatially visualise the landscape in order to demonstrate pressures and impacts in the terrain
  • Visualise how geomorphological processes and features are interacting in a landscape
  • View temporal changes in landforms and fluvial features
  • Map the location of a feature to help determine why it is there, what it is composed of and how it can be changed through hydromorphological processes (Otto & Smith, 2013)

2. Method summary[edit]

Geomorphological mapping is an important technique for the documentation and reconstruction of landscapes. In recent years it has evolved from a purely field-based exercise, to one that is heavily technologically reliant. Geographical Information Systems (GIS) have allowed developments in geomorphological mapping to progress, enabling more high-resolution mapping and visualisation of landscapes. This is useful to highlight features and issues, prioritise works and monitor adaptation of environments to restorative actions.

Remote sensing data and Digital Elevation Models (DEMs) are also useful techniques for visualising the data and analysing terrain, pre- and post-restoration. Monitoring the landscape over time provides a picture of how a catchment is changing and adapting to works across large scales.

Monitoring the development of a restoration project through mapping the site is a beneficial method for spatially visualising the temporal changes across a landscape.

Different types of maps – (Otto & Smith, 2013):

  • Basic – show all observed features of a landscape
  • Derived – focus on one particular theme or practical application i.e. NFM

Field mapping and drawing on site can capture more detail and provide more accuracy, as the surveyor can see features on the ground and interpret condition, dimensions, and state of the environment through direct observation in the field. This avoids opening up the potential for less accurate interpretation by analysing secondary data and imagery. Although this is subjective and biased by surveyor ability, it allows the surveyor to gain a first-hand understanding of the landscape (Otto & Smith, 2013).

2.1 Method for field mapping using GIS[edit]

(Otto & Smith, 2013)

Figure 2: Example of Geomorphological Mapping (Otto & Smith, 2013)

Pre-fieldwork preparation

  • Identify area or site to be mapped and the purpose of the map. Think about whether the map is based on an area of interest, or the restoration technique that will be installed. Think about recreating this map post- works, and the areas which may be impacted
  • Gather as much secondary map data as possible including geology maps, historical maps and any other datasets necessary for the final map
  • Generate a GIS database to store layers
  • Develop a guide for what and how the landscape will be mapped and features will be represented
  • Map major forms and features using remote sensing data

Field work

  • Survey the area of interest, taking notes or drawings of any features, as well as their condition, dimensions and possible impacts on other aspects of the channel
  • Track locations of points of interest using a GPS
  • Capture features with photographs and videos

Post mapping activities and map production

  • Add to the GIS database by inputting details and other features to the dataset
  • Compare the previously collected remote sensing data, and observed field data in order to validate remote data
  • Use GIS to produce final geomorphological map, remembering to highlight the main features or issues you were aiming for

3. Advantages[edit]

  • Mapping all the geomorphological features in a catchment highlights areas of erosion and deposition to help identify issues and prioritise reaches
  • Indicates how dynamic the river system is, and highlights potential sources of silt or slower flow which may influence pressures locally
  • Understanding the dynamicity of a river will assist in selecting the most appropriate restoration methods to use and give an indication of where monitoring sites should be located

4. Limitations[edit]

  • Caution when interpreting map legends to ensure accurate understanding, due to poor standardisation of information across disciplines

5. Recommendation for method application[edit]

  • Set out clear, meaningful aims for the map to maintain purpose (Otto & Smith, 2013)
  • If drawing and mapping features in the field by hand, it is useful to have a printed map of the area on a clipboard. Use tracing paper over the top of this map to draw and accurately locate features observed in the field

6. Costs[edit]

Much secondary data can be downloaded free of charge such as LiDAR data. Survey costs will include purchase of a GPS, and labour costs.

7. Data analysis[edit]

GIS can be used to view, store and analyse spatial data. Spatial analysis tools and functions are available to manipulate data to show certain features or highlight issues. Open Source software QGIS can be download and used free of charge.

8. References[edit]

  1. Otto, J-C. & Smith, M. J. (2013) ‘Geomorphological mapping’, Geomorphological Techniques, 2, section 6. Available at : https://www.geomorphology.org.uk/sites/default/files/geom_tech_chapters/2.6_GeomMapping.pdf
  2. Seijmonsbergen, A. C. & de Graaff, L. W. S. (2006) ‘Geomorphological mapping and geophysical profiling for the evaluation of natural hazards in an alpine catchment’, Nat. Hazards Earth Syst. Sci., 6, pp 185-193. Available at : https://www.nat-hazards-earth-syst-sci.net/6/185/2006/nhess-6-185-2006.pdf