Geoscience Reference
In-Depth Information
3200
(a)
100%
0%
(b)
120
20%
0%
90%
0%
(c)
(d)
Figure 3.2
An overview of selected
attributes characterizing rivers and streams
in England and Wales in 2007-2008: (a) the
severity of channel modification, using
Habitat Modification Score; (b) the
percentage of river bed and banks
resectioned; (c) the percentage of river bed
and banks reinforced; (d) the distribution of
treeless rivers and streams (percentage of
500 m river lengths without trees);
(e) the distribution of Himalayan balsam;
(f) the distribution of Japanese knotweed -
(e) and (f) expressed as the percentage of
500 m river lengths at which these species
were found. Maps interpolated from the
4849 baseline RHS sites - see 'Methods' for
full explanation.
(e)
(f)
70%
0%
30%
0%
Table 3.1
Channel and bank modification at the 2007-2008 RHS baseline survey, showing 'minor watercourse'
(1:50 000 scale map sites) and 'core' (1:250 000 scale map sites) sample sites. Figures represent percentage of sites in
each Habitat Modification Class.
Habitat Modification Class
'Minor watercourse' sample
'Core' sample
Combined total
1: near-natural
8.7 (
n
=
149)
10.8 (
n
=
341)
10.0 (
n
=
490)
2: predominantly unmodified
10.4 (
n
=
178)
15.7 (
n
=
498)
13.8 (
n
=
676)
3: obviously modified
9.2 (
n
=
158)
13.0 (
n
=
413)
11.7 (
n
=
571)
4: significantly modified
20.8 (
n
=
358)
20.0 (
n
=
633)
20.3 (
n
=
991)
5: severely modified
50.9 (
n
=
875)
40.5 (
n
=
1281)
44.1 (
n
=
2156)
