Reach characterisation

Reach

Aim

Characterisation of river energy, channel and floodplain dimensions, morphology /geomorphic units, sediments, vegetation and physical pressures, including:

• Quantification of channel dimensions
• Stream power
• Bed and bank sediment calibre
• Vegetation extent and structure / patchiness
• Pressures, particularly on lateral connectivity.

Data layers and hydromorphologically relevant parameters

Remotely-sensed data sets (including Google Earth) can provide much of the basic information on channel dimensions, hydromorphological and vegetation features (geomorphic units) and sometimes a crude indication of bed material size. Flow information is drawn from the segment scale.

DEMs provide reach slope estimates.

Where available, Lidar surveys provide very accurate information on channel slope, channel-floodplain morphology and width, and riparian vegetation distribution, height and structure.

Potential data sources

• Google Earth
• Orthophotos
• Multi-spectral remotely-sensed data
• Digital Elevation Models (e.g. EU-GDEM)
• Lidar data
• Pan-European and National vegetation databases

Characteristics

Channel dimensions

Channel dimensions: (1) Average reach and channel gradients; (2) Bankfull and baseflow channel width; (3) Bankful and baseflow channel sinuosity index (4) Braiding index (5) Anabranching index

River energy

River energy: (1) total stream power; (2) specific stream power; (3) average bed shear stress

Bank and bed sediment

Sediment size: (1) Bedrock exposure; (2) Composition (>64 mm); (3) Composition (<64 mm)

Riparian and aquatic vegetation

Riparian vegetation: (1) Age structure; (2) Lateral structure; (3) Patchiness; (4) Species

Large wood: (1) Large wood presence and abundance

Aquatic vegetation: (1) Extent; (2) Patchiness; (3) Species presence and abundance

Physical pressures and impacts

River bed condition: (1) Bed armouring (gravel-bed rivers); (2) Bed clogging / burial (gravel-bed rivers); (3) extent of bed reinforcement; (4) number of channel blocking structures; (5) sediment, wood, vegetation removal

River bank condition and lateral continuity: (1) hard bank reinforcement; (2) bank edge levées/embankments; (3) set-back levées/embankments; (4) bank top infrastructure; (5) immobilised river margin; (6) actively eroding river margin; (7) width of erodible corridor; (8) number of channel-crossing /blocking structures

Riparian corridor connectivity and condition: (1) floodplain accessible by flood water; (2) riparian corridor accessible by flood water; (3) riparian corridor affected by intense woodland management activities; (4) abundance of alien, invasive plant species; (5) extent of impervious cover, severe soil compaction, excavations / extractions / infilling

More details on the characterisation of reaches can be found in chapter 5 of Deliverable 2.1.