Chapter 6 . Stream Assessment
103
CI)
1
u
0.9
c
CI)
0.8
11)
0.7
CI)
... 0.6
c.
- 0.5
0
>- 0.4
:!::
0.3
.c 0.2
IV
.c 0.1
...........
/
K
/
/
90%
/
proteetion
/
~
level
...--.0
0
...
Q.
3
4
5
6
7
8
9
10
Dissolved oxygen (mg/I)
Fig. 6.9. The impact of dissolved oxygen on the probability of presence of
Gammaridae and the 90% protection level (7% of dissolved oxygen).
6.3.2.2.2
Feasibility Analysis of River Restoration Options
An illustration about the application of ANN models to mitigate human impacts
on the Bettelhovebeek is presented in this case study. Several structural
modifications are dramatically affecting the biological communities at this site.
Tab. 6.3. Optimal restoration option for the Bettelhovebeek and predicted
macroinvertebrate taxa and BBI after river restoration.
Structural
Before river restoration After river restoration
characteristics
Actual bad situation
Future good status
Artificial embankments
concrete and iron str.
none
Meandering
none
moderate
Deep/shallow variation
none
moderate
Hollow river beds
none
weil develoQed
Macroinvertebrate taxa
Actual bad status
Future good status
(field measurement)
(ANN eredidion)
Sialis
absent
present
Limnephilidae
absent
present
Simuliidae
absent
present
Belgian Biotic Index
moderate
quality good quality (BBI=7)
(BBI=S)