Geology Reference
In-Depth Information
13
Modelling the Role
of Vegetated Buffer Strips
in Reducing Transfer of Sediment
from Land to Watercourses
J.H. DUZANT
1
, R.P.C. MORGAN
1
,
G.A. WOOD
2
AND L.K. DEEKS
1
1
National Soil Resources Institute, Cranfield University, Cranfield, Bedfordshire, UK
2
Integrated Environmental Systems Institute, Cranfield University, Cranfield, Bedfordshire, UK
13.1 Introduction
for example the Environmental Stewardship
scheme (Defra, 2005). Among the options avail-
able is support for planting vegetated buffer
strips or barriers.
The term buffer usually describes a vegetated
strip placed between a river, stream or creek
and an adjacent upland land-use activity
(Hickey & Doran, 2004) to protect water qual-
ity and act as a nutrient filter (Nieswand
et al
.,
1990). The main functions of the buffer are to
reduce surface runoff, filter sediment, promote
infiltration of water into the soil and ground-
water, and protect the river bank against ero-
sion (Muscutt
et al
., 1993). In addition, the
buffer provides a habitat and a wildlife corridor
for fauna and flora (Parkyn, 2004). Buffers can
also be placed on hillslopes to control erosion
in upstream areas closer to the sediment source.
They often comprise vegetated barriers, usually
on or close to the contour, where they perform
similar functions to the riparian barriers but
they are usually much narrower, often only 2 to
6 m wide and rarely more than 25 m wide (van
Dijk
et al
., 1996). The other major difference is
that runoff leaving the barrier passes on to land
downslope instead of discharging into the
watercourse.
Vegetated buffer strips at the edge of arable fields
have been shown to trap as much as 70-90% of the
inflowing sediment (Dillaha
et al
., 1987; Magette
Phosphorus is normally the primary limiting
factor in the process of freshwater eutrophica-
tion. In the United Kingdom more than 50% of
the phosphorus entering surface waters is
derived from agriculture and, on arable land, as
much as 80% of this is in particulate form
(Defra, 2002). This means that controlling the
transfer of sediment from agricultural land to
water bodies is an important component of the
protection of the aquatic environment. Sediment
control is therefore a policy issue for the UK
government if it is to meet the requirements set
out in the European Water Framework Directive,
the European Freshwater Fish Directive, the
European Habitats Directive and the Convention
for the Protection of the Marine Environment
of the North-East Atlantic (OSPAR) (Owens &
Collins, 2008). In response, various schemes
with financial support have been made avail-
able to farmers to manage land in environ-
mentally responsible ways, including the
Agri-Environmental Schemes and Single Farm
Payment Schemes supported by the Department
for Environment, Food and Rural Affairs (Defra),
