Channels

Cards (13)

  • 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=Dd =Ltot/A 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