Brandt, Steffen
4 WATERCOURSE NETWORK
4.1 Structure of the Route System
By extracting from the terrain model, all hydrologic relevant elements were used by the ArcInfo module Dynamic
Segmentation to reconstruct a three-dimensional water course network (route system) representing the water flow status
at the date of fly. The module also generates event tables labelled with descriptions of the watercourse.
The routes of the individual waterway axes and slope edges are set for one waterway at a time in three route systems
(beds, slope edges to the left of the direction of flow
. Slope edges to the right of the direction of flow) with the
compilation of the appropriate Route Attribute Table (RAT) and Section Table (SEC).
As a rule, the stationing corresponds with the real length of the waterway and is set — beginning with 0 meters at the
mouth — against the natural direction of flow. The determination of this natural direction of flow is sometimes difficult,
Since many watercourses no longer show a clear direction of flow throughout their entire course as a result of
subsidence which has already occurred in recent decades.
In some cases — especially principle drainage channels — stations of the channel floor already exist (e.g. by the water
board responsible), which do not always reflect the true length of the watercourse. For the illustration of this fixed
station, dynamic segmentation offers a large number of ways in which all previous situations (e.g. swelling/lineation for
an entire waterway or stretches of it, stationing with faults) can be put into practice without difficulty.
Figure 6. Detailed view of the construction elements
for DTM and watercourse network (DTM grid and
breakline points: green, channel floor points: magenta,
watercourse axis: thick blue line, flood-relevant slope
tops: thinner blue line, triple points: red line)
Finally, all slope edges must be stationed in
dependence on the corresponding channel floor using
allocation elements, referred to as triple points (cf.
Figure 6). ;
These route systems now represent the two-
dimensional status of the watercourse network and the
flood-relevant slopes at the date of flight. The course
corresponds exactly with the breaklines of the DTM.
A third dimension is added to the two-dimensional
watercourse network by classifying the respective
elevations from the DTM for all route points in a joint
point event table.
As described in Chapter 2, underground extraction
leads to subsidence at the surface. For the assessments
and forecasts within the environmental compatibility
survey and the water resource and ecological
assessment the expected subsidence must therefore be
calculated on the basis of the valid extraction plans for
a number of clearly defined periods until approx. 2020.
The starting point for this is always the date of flight.
For these periods the DTM stage 2 is lowered whilst
retaining all linear structures. All points of the three-
dimensional watercourse network are also linked with
these subsidences, and the point event table is extended
by the corresponding elevations of the individual
periods. Between the date of flight and start or finish of
the extraction to be authorized, geometric changes in
the waterways can take place due to binding
watercourse development plans (e.g. deepening,
displacement) — both in the location and in the altitude.
These changes are also taken into account in the
respective DTMs and watercourse networks.
This can lead to the definition of new routes in the
route systems. At the same time, old routes must no
longer be considered for other periods.
To enable this period-based observation, the RATs of the watercourse network are supplemented with details of the
validity of a route.
218 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000.
