Derive, modify and plot the stream network

The stream network is a subset of the flow network. Often, this subset is defined as having a minimum upstream area. The idea is that if upstream area exceeds a critical value than flow becomes channelized in stream networks.

StreamObject stores stream networks. Here we simply assume that streams initiate at upstream areas greater than 1000 pixels.

import topotoolbox as tt3
import matplotlib.pyplot as plt

dem = tt3.load_dem('tibet')
fd  = tt3.FlowObject(dem);
s   = tt3.StreamObject(fd,threshold=1000,units='pixels')

Plot the stream network

The stream network can be plotted using the plot method on StreamObject.

fig, ax = plt.subplots()
dem.plot(ax,cmap="terrain")
s.plot(ax=ax,color='r');

Modify the stream network

Frequently, we might be only interested in parts of the river network. StreamObject has a number of methods that can modify the geometry of the network. For example, we may be interested in only the largest basin.

s2 = s.klargestconncomps(1)
st = s2.trunk()
fig,ax = plt.subplots()
dem.plot(ax=ax,cmap="terrain")
s.plot(ax=ax, color='r')
s2.plot(ax=ax,color='k')
st.plot(ax=ax, color='b')

<Axes: >

Plot the longitudinal stream profile

Applications in tectonic geomorphology are often interested in longitudinal profiles and features such as knickpoints. Visual inspection of the profile provides a first clue for these features.

fig = plt.figure()
ax = plt.axes(xlabel="Distance (km)", ylabel="Elevation (m)")
st.plotdz(dem, ax=ax, dunit='km')
ax.autoscale_view()