Channels

• surface of catchment can be divided in land and water
• channel network is result of landscape formation in past and preferred route for water flow in present
• changes affect both flow of water towards channels and flow in channels and alter discharge regime of river
• drainage density Dd (km/km2) quantifies abundance of channels
• $Dd =$$Ltot/A$

  • Ltot (m) = total length of all channels
  • A (m2) = area
• high drainage density indicates that certain area contains many channels per km2 so water only has to travel short distances over and through ground to reach surface water network
• drainage densities high in areas with low soil conductivity
• most common channel network pattern is dendritic pattern because it is most efficient in transporting variety of substances
• patterns and their landscapes

  • dendritic: landscapes with homogenous geological formations with many tributaries
  • radial: streams start at one point and flow in all directions often seen on volcanoes or mountains
  • trellis: found in areas with folds in earth crust with relatively large number of channels that have same direction on each side of river
  • parallel: occurs on steep slopes where water flows downhill fast
• channels located in headwater (upstream) of catchment behave differently than channels located downstream
• Strahler order numbering

  • exterior links get order 1
  • when two links of same order meet, add 1
  • when to links of different orders meet, keep highest order
  • outlet is endpoint with highest order (represents Strahler order)
• source: location upstream where channel starts
• channel network can be derived from DEM assuming certain drainage density