A12. Pressure flyover survey

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1. Objectives[edit]

  • To identify and record the presence, absence and extent of hydromorphological pressures.
  • To rapidly collect data on morphological pressures

2. Method summary[edit]

The flyover survey uses aerial photography (such as Google Earth) combined with Google Street View to identify and record hydromorphological pressures such as weirs, realignment and bank protection. Surveyors record data in an excel spreadsheet form for each reach in their catchment. The approach follows the following general steps:

  1. Add the river network and any pressure datasets to Google Earth.
  2. Zoom into the reach that you will be assessing.
  3. Look up and down the reach to assess the level of visibility you have.
  4. Fill in the form by starting upstream and working downstream.
  5. Record the planform type and valley confinement.
  6. Record the modifications present such as structures, bank modifications and embankments.
  7. Record the land use type for 10m and 50m from the bank-top.
  8. Look at 360 degree photos at road crossings if available to assist your assessment.

The type of data recorded includes 'counts' for structures such as weirs, culverts and crossings; and 'extent' (None (0-1%), Present (1-33%), Extensive (≥ 33%)) for modifications that have a length element such as bank protection, embankments and resectioning.

3. Advantages[edit]

  • Quickly collect data over large areas.
  • Particularly good for assessments where resources and time does not allow site visits.
  • Data aligns with established methods such as River Habitat Survey.

4. Limitations[edit]

  • Tree cover and vegetation can result in poor visibility on aerial photography.
  • Some modifications are hard to see if 360 photos are not available.