Environmental Engineering Reference
In-Depth Information
Mitigation of impacts
many UK catchments, so would have to be
taken into account (a formidable challenge) when
assessing evidence that changes to local runoff
generation processes have affected flooding at the
catchment scale.
Historical rainfall runoff datasets have been
analysed to look for impacts of land use and
management change on flood generation (Beven
et al. 2008), for a set of six predominantly rural
catchments (75-1134 km
2
) which (i) were con-
sidered to be candidate catchments where land
use management impacts might have taken
place, and (ii) had reasonably long rainfall and
runoff records available. No clear evidence for
significant impacts was found, but this does not
necessarily mean that impacts do not exist, only
that they were not detectable for the catch-
ments analysed, given both the natural variabil-
ity of the climate and the inadequacies of the
available data in characterizing the hydrological
response.
Interventions can mitigate or avoid the impacts
of land use management on local flooding. The
majority of these interventions are aimed at
source control of on-farm runoff through the use
of good land use management practices. For ex-
ample, for maize cropping, particularly in free-
draining loamy, silty and sandy soils, ploughing in
the autumn and spring can reduce field plot runoff
significantly (Kwaad and Mulligen 1991; Martyn
et al. 2000; Clements and Donaldson 2002). The
success of other management techniques such as
direct drilling, cover crops and soil mulches ap-
pears to bemuchmore uncertain and dependent on
soil type (Charman 1985; Schafer 1986; Auerswald
1998; Melville and Morgan 2001; Clements and
Donaldson 2002).
Desirable management practices for mitigating
field-scale runoff generation are depicted in
Figure 2.2. Most require careful targeting with
Fig. 2.2
Potential for integrated runoff control to reduce flood risk, pollution and erosion.
