Geoscience Reference
In-Depth Information
[mm]
t
= 0 s
[mm]
t
= 130 s
Crest
200
z
200
z
Pilot channel
100
100
0
0
1000
1000
800
1000
800
1000
600
800
600
800
600
600
400
400
400
400
y
200
y
200
200
x
200
x
00
00
[mm]
t
= 80 s
[mm]
t
= 330 s
200
z
200
z
100
100
0
0
1000
1000
800
800
1000
1000
800
800
600
600
600
600
400
400
400
400
y
y
200
200
x
200
x
00
00
200
Fig. 4 Three-dimensional (3D) breach profiles at various times
t
with time, in accordance to Coleman et al. (
2002
). During the entire test, the projected
grid was recorded with a frequency of 1 Hz and afterwards evaluated using the
AICON software. The quality and integrity of the breach profile depend essentially
on the detected grid points of an image. There are several reasons that may disturb the
visibility of the grid points and impede an automatic computer computation:
l
Sediment colour changes as it gets wet. The contrast between the sediment and
the projected grid varies therefore during the test.
l
The projected grid is partly distorted due to inclined dike surfaces and the
projector position.
l
Light of projector is reflected on water surface, especially at large times under
high outflow discharge. These reflections disturb the visibility of the sediment
surface.
l
Surface waves and suspended sediment may complicate the grid point detection
due to reduced visibility (Fig.
5a
).
l
Breach side slope may be steep and grid detection therefore fails as the vertical
displacement of the grid points is too large.
However, the first evaluations are surprisingly good, given the various factors
disturbing the proper grid recording. A non-intrusive method is therefore available
in principle to determine a sediment surface topography during a spatial dike breach.
To increase grid visibility and to improve the automatic computation, the test setup
is currently optimised. Further steps include a test series to account for the record-
ing accuracy and a detailed analysis of the breach formation.
4 Conclusions
The videometric measurement system of AICON
®
3D Systems Ltd. was used to
determine the three-dimensional breach profiles during a spatial dike breach. This
system allows for recording a breach sediment surface through the water surface
