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