Project summary

1
Project summary

• PE0205
• The strategic placement and design of buffering
  features for sediment and P in the landscape
• Project team Alison Collins, Julia Duzant,
  Gavin Wood, Phil Owens, Roy Morgan Tim Brewer
• a.j.collins_at_cranfield.ac.uk
• Sept. 2003/Aug. 2006

2
Project objectives

• To determine the potential effectiveness of
  features within current or future
  agri-environment schemes for the trapping of soil
  and P, with the consideration of any potentially
  better options that are currently not included
  within schemes
• 2. To identify where in the landscape buffer
  features could be most effectively placed whilst
  avoiding/minimising detrimental effects to
  landscape quality

3
Objectives cont.

• To develop mechanisms by which this strategic
  placement could be determined by local Defra
  staff, advisors/consultants and farmers
• To consider the most appropriate design of
  buffers for trapping sediment (whilst maintaining
  the intended biodiversity benefits of the
  agri-environment schemes and not degrading
  landscape quality)
• To calculate the cost effectiveness of the
  proposed most useful options in terms of
  potential costs per kg of pollution prevented.
  Assess the costs to both Government (scheme
  grants) and farmers (profits forgone, cost of
  implementation and maintenance, scheme grants) of
  these options

4
Project team

• NSRI
• Alison Collins Project manager/Lab studies
  advisor
• Gavin Wood Tim Brewer GIS/Spatial component
  advisor
• Phil Owens Field studies advisor
• Julia Duzant Project scientist involved in
  day-to-day management of all project components
• Roy Morgan Technical adviser (soil erosion,
  control and role of vegetation)
• Dedicated technician in process of appointing
• Steering group
• Provide perspectives from policy, practice, and
  end user communities
• Ensure relevance of detailed research programme
  to the national context of concerns over P,
  sediment and the environment
• Provide technical and scientific advice
• Provide external quality control
• Act as dissemination routes for project outputs
• Provide linkage with other P and sediment related
  research

5
Project components/activities necessary to
satisfy objectives

• Desk based literature review
• Laboratory experimental programme (JHD)
• Field reconnaissance, ground-truthing and
  sampling (PNO)
• GIS development, validation, scenario analysis
  and spatial modelling (GAW)
• Economic analysis (AJC)
• Dissemination activities

6
Desk-based literature review

• Sources
• Buffer performance from both empirically derived
  sources and practice
• Material from UK, Europe, and USA
• Review other relevant Defra funded research such
  as Review of P retention at the field and
  catchment scale (NT1030)
• Outputs
• General context and lit. review
• Profile for each agri-environment scheme feature
  (Objective 1 5) including
• likely buffer functions,
• main biophysical properties,
• buffer effectiveness,
• perceived environmental,
• spatial and temporal constraints,
• ideal location/context,
• opportunities to combine with other buffers/land
  management practices,
• cost-effectiveness for a range of objectives
• and farmer perception of feasibility, cost and
  existing use

7
Laboratory component Tri-axial soil slope

• 6 x 3 m soil surface
• Pressurized rainfall simulators
• Simulation of a range of rainfall simulators

• 0.3 m soil depth
• Linear, convex and concave slopes
• Up to 20 slope angle

8
Lab component

• To derive empirically based relationships between
  biophysical parameters, such as (Objective 4)
• Above ground architecture (height, width,
  uniformity, branching)
• Below ground architecture and effects (root
  density, depth, branching and the effect on
  vegetation stability and subsurface flows)
• Material behaviour (bending stress, roughness,
  resilience over flows and sediment loads)
• Buffer effectiveness (Objective 4)
• how much sediment is trapped (in respect of the
  fraction most likely to associate with P)
• where the sediment is being trapped in relation
  to the buffer eg within or upslope
• the effect on the downward movement of P through
  the soil
• the effect of buffers on the movement down slope
  of P in surface run-off and infiltration rates
  adjacent to buffer features

9
Laboratory programme

• The laboratory programme will comprise a
  factorial experiment for the following
  treatments
• Control bare soil
• 2 slope angles
• 2 buffer widths
• 2 soils (sandy loam, clay loam)
• Possible treatments
• 2 vegetation types/species and a complex of the
  two
• 2 buffer heights
• 2 density plantings
• 2 buffer designs/structures/architecture of
  leading edge
• Addition of P source

10
Measurements

• Buffer properties and effectiveness will be
  determined through a series of point samples and
  measurements on the soil flume taken before and
  following simulated storm events
• Soil moisture content
• Sediment and P distribution
• Infiltration capacity
• Surface micro-topographical changes
• Characteristics of deposited material
• Enrichment ratios
• Analysis of runoff and sediment for total P,
  dissolved P, particulate P, total runoff, total
  sediment and particle size distribution.

11
Field component

• 4 visits per year, in respect of seasonal
  variations, over 2 years in the Parrett
  catchment, Devon
• Building on existing data held within NSRI
• Vegetative buffers
• Volume of soil trapped by buffers
• Soil samples will be taken above, below and where
  possible within the buffer feature.
• Small Astroturf mats will be used to trap
  sediment/calculate indicative sedimentation rates
• Field auger samples will be taken at points
  within and adjacent to the buffer features -
  particle size distribution and P analysis.
• Bulk density cores to extrapolate infiltration
  rates within and around buffer features.

12
Non-vegetative buffers

• Potential for sediment settling and P retention
  by hedgerows, farm yard ponds, wetland areas,
  floodplains and in-channel features
• Information on the role of hedgerows (including
  non-vegetative features such as walls) using the
  Astroturf mat approach
• Investigations of lake sedimentation and the
  residence time of water in the lake/pond,
• Floodplain buffer effectiveness will also be
  estimated using Astroturf and point sampling
  methods - Sample collection cross-referenced
  with over bank flood incidences from local
  records, and simple fingerprinting technologies
  will be employed to separate over bank events
  from land-derived sediment.

13
Specific outputs of lab and field component

• Understanding of micro and macro-scale operation
  of buffer features in landscape and mapped areas
  of deposition and sediment type in relation to
  the buffer feature and hydrological pathway
  (Objective 2)
• Determination of the most critical biophysical
  and non-biophysical parameters (Objective 4)
• Understanding of the performance of buffer
  features in the context of environmental, spatial
  and temporal variations using lab results
  validated by field observations (Objective 1 2)
• Design guidance that details geometrical,
  hydrological and biophysical properties for
  optimum sediment and P trapping and retention in
  non-vegetative buffer features (Objective 1 4)

14
GIS component

• Aim
• To develop a spatial GIS-based model to establish
  the strategic placement of buffer features within
  the landscape

• Field data from the Parrett catchment will
  provide ground truthing of input data for the GIS
  model

Laboratory results will be used to describe the
behaviour of the buffer features as mapped within
the GIS
15
Model development

• Initial phase GIS modelling of multiple flow
  pathways (surface run-off routing) based on high
  resolution digital elevation models. Overlaying
  field boundaries, drainage networks (and
  sub-surface pathways and drains) and existing
  buffer features to identify interruptions and
  diversions to natural hydrological pathways.
• Second phase potential erosion estimation using
  established physical erosion models and relating
  this to accepted levels of associated phosphorus.
  Adjustment of model to account for particle size
  selectivity of particulate P.

16
Surface flow pathways
17
Contributing areas
18
GIS model

• The model will be used to assess alternative
  landscape arrangements of buffer types and
  locations. Scenario analysis will be performed
  using base data from a selected catchment (e.g.
  Slapton, Devon, or other that is used within P
  research) as an independent case study. Outputs
  used to establish effectiveness of buffer type
  and location, in addition to providing model
  validation (Objective 2).

19
Cost benefit analysis

• Outputs from project components

Selected set of most effective buffers
Estimation of the cost of the features to
buy/implement ( time)

• Against gains
• Kg of P transfer prevented per contributing area
• Assimilation and/or processing of the various
  forms of P
• Type of material buffered e.g. fine sediment and
  the associated nutrient risk
• Impact on other types of pollution such as
  reduced flood risk
• Ecological benefits

Matrix of cost effectiveness for selected buffer
features (Objective 5)
20
Dissemination activities

• Sequence of peer-reviewed journal papers
• Publication in trade magazines and NSRI outlets
  (e.g. e-zine)
• Dedicated website
• Farmer focus group?
• CD-ROM/handbook design guide and strategic
  placement
• Workshop at end of project
• Links in other websites e.g. www.fwag.org.uk (any
  others?)
• Dissemination via steering group
• Defra P review activities

21
Milestones
22
Specific project outputs

• Evaluative review of potential buffer
  effectiveness within agri-environment schemes
• A design guide for key vegetative and
  non-vegetative buffer features
• A simple model and decision support system for
  strategic placement of buffers
• Recommendations for optimising buffer performance
  over time and space via maintenance activities
• A matrix of cost-effectiveness for key buffers
• A workshop to disseminate project products
• Dedicated project website
• Publications in scientific journals, trade
  magazines and popular press