Download The challenges of innovative soil erosion control and management

Innovative methods of
soil erosion control
Royal Society of Chemistry
21st January 2013
Jane Rickson
Professor of Soil Erosion and Conservation
National Soil Resources Institute (NSRI)
School of Applied Sciences
Cranfield University
Outline of the talk
• Attitudes to soil
• The role of soil chemistry
Soil erosion in Ross on Wye, 2009
• The importance of soil
• Threats to soil resources
• Soil protection - Innovative and practical solutions
• Geotextiles for soil erosion control
• Concluding thoughts
1. Attitudes to soil
• “….And what do you do for a living?”
• Soil’s poor “PR”:
• ‘mud’ used in a figurative sense meaning worthless or
polluting (16th century)
• ‘mudslinging’
• ‘drag his name through the mud’
• ‘His (her) name is mud / Mudd’
• ‘stick in the mud’
• Connotations of the word “soil”
http://www.visualthesaurus.com/app/view
1. Attitudes to soil
• Cultural context
• Soil science (more later)
….and the arts
1. Attitudes to soil
“The thin layer of soil covering the earth's surface
represents the difference between survival and
extinction for most terrestrial life.”
From: Doran, J.W. and T.B. Parkin. 1994.
Defining and assessing soil quality.
In J.W. Doran, D. C. Coleman, D.F.
Bezdicek and B.A. Stewart (eds.),
Defining Soil Quality for a Sustainable
Environment. Soil Science Society of
America.
2. The role of soil
chemistry
• Soil chemical properties
•
•
•
•
Carbon
Nutrients
Trace elements
pH
• Chemical processes in soils
• Carbon and nutrient cycling
• Carbon storage
• Gaseous emissions (greenhouse gases etc)
2. The role of soil
chemistry
The Carbon Cycle
http://www.gfdl.noaa.gov/anthropogenic-carbon-cycle
2. The role of soil
chemistry
http://www.tececo.com/sustainability.role_soil_sequestration.php
The Soil Carbon Cycle
3. The importance of soil
1.
Can 9 million people be fed
[and housed and transported]
equitably, healthily and
sustainably?
2.
Can we cope with future
demands for water?
3.
Can we provide enough energy
to supply the growing
population coming out of
poverty?
4.
Can we mitigate and adapt to
climate change?
5.
Can we do all of this and
reverse declining biodiversity
and loss of ecosystems
Sir John Beddington, Chief Scientific Advisor to HM Government, Foresight Report; “The Perfect Storm”
3. The importance of soil
1.
Can 9 million people be fed
[and housed and transported]
equitably, healthily and
sustainably?
Can soil address these challenges?
2.
Can we cope with future
demands for water?
3.
Can we provide enough energy
to supply the growing
population coming out of
poverty?
4.
Can we mitigate and adapt to
climate change?
5.
Can we do all of this and
reverse declining biodiversity
and loss of ecosystems
Sir John Beddington (Chief Scientific Advisor to HM Government) “The Perfect Storm”
3. The importance of soil
• Soil provides vital ecosystems goods and services (or “functions”)
Ecosystem service
Examples
Provisioning of
material goods and
services
Agricultural production (food, fibre, fodder, fuel)
Water storage and supplies
Land for development (residential, industry, infrastructure)
Regulation of
ecosystem processes
Flood control (water storage)
Carbon storage (CO2 emissions: mitigate climate change)
Cultural, non-material
services
Landscape aesthetic
Recreation / amenity, protection of heritage
Supporting services
Habitats, biodiversity
Soil formation
• Sustainability (economic, environmental and social pillars)
• Human health and wellbeing (Millennium Ecosystem Assessment)
• Individuals’ and national economic status
3. The importance of soil
1.
Can 9 million people be fed
[and housed and transported]
equitably, healthily and
sustainably?
Soil has a role in addressing
these challenges…however…….
2.
Can we cope with future
demands for water?
3.
Can we provide enough energy
to supply the growing
population coming out of
poverty?
4.
Can we mitigate and adapt to
climate change?
5.
Can we do all of this and
reverse declining biodiversity
and loss of ecosystems
4. Threats to soils
and their functions
• As identified in the EU Thematic Strategy
for Soil Protection (2006)
•
•
•
•
•
•
•
•
•
Soil erosion*
Compaction
Loss of organic matter
Surface sealing
Contamination
Loss of biodiversity
Salinisation
Acidification
Landslides
4. Threats to soils
and their functions
“Soil degradation involves both the physical
loss (erosion) and the reduction in quality of
topsoil, associated with nutrient decline and
contamination. It affects soil quality for
agriculture and has implications for the
urban environment, pollution and flooding.
Currently, 2.2 million tonnes of topsoil is
eroded annually in the UK and over 17% of
arable land shows signs of erosion.
This POSTnote examines the…challenges
and opportunities for soils in a changing
climate. These include the potential for
using degraded and polluted soils in the
built environment for brownfield
redevelopment as well as the possibility of
using soils to mitigate carbon emissions.”
4. Threats to soils and
their functions
Example: Soil erosion in England & Wales
&W
Typical erosion rate
range (t ha-1 year-1)
Land use affected
Exported off field
Wind erosion
Tillage
erosion
Co-extraction with root
crops and farm machinery
Water
0.1 – 2.0
0.1 – 10.0
0.1 – 5.0
0.1 – 15.0
Arable
Arable
Arable,
pasture,
upland
No
Yes
Yes
Arable,
upland,
some
pasture
Yes
Comparison of the magnitude of soil loss for different erosion processes (Owens
et al., 2006). N.B. Rate of soil formation ≈ 1 t ha-1 year-1 (Verheijen et al., 2009)
4. Threats to soils
and their functions
Estimated annual costs of soil erosion
to UK economy in £million
(2000 prices)
£ million
% contribution
from agriculture
Soil organic loss, leading to carbon
dioxide loss
74
95%
On-farm costs (additional fertilisers, etc.)
8
100%
Accidents/stream channels (i.e. off-site
costs mainly related to clean-up
operations)
8.2
95%
Effects on flooding
115
14%
TOTAL ANNUAL COST (£ million)
205
Source: Environment Agency 2002. Agriculture and natural resources: benefits, costs
and potential solutions. Bristol.
What can be done?
5. Innovative and
practical solutions
Engineering measures
Field structures
Terraces
Storm water drains
Cut off channels
Lined waterways
5. Innovative and
practical solutions
Soil management measures
Use of tillage and cultivation practices
direction of tillage operations
residue management
conservation tillage (minimum till, zero till)
Use of soil amendments
Soil conditioners
Organic matter additions
5. Innovative and
practical solutions
Agronomic measures
The use of vegetation and simulated vegetation
• Mulches
• Geotextiles
“Bioengineering” practices
Geotextiles
• Definition:
“a permeable textile materials, used with foundation, soil, rock, earth
or any geotechnical engineering related material”.
• Not a new technique
• ancient Egypt - use of cotton to reinforce building materials
• use in civil engineering increased in 1960s
• availability of cheap, synthetic textiles
• rapid urban and infrastructural development and expansion
• implications for world trade and economic development
Geotextile
applications
• Applications
• Separation
• Filtration
• Drainage
• Soil reinforcement / slope stability enhancement
• Soil erosion control*
• Vegetation management
Total global geotextile market ≈
1000 million m2 per annum (2000 data)
Geotextiles for
soil erosion control
• Fibres used
• woven
• non-woven
• knitted
• Structure of geotextiles:
•
•
•
•
Mats
Webs
Grids
Sheets
• Two or three dimensional
• Natural versus synthetic
• Buried or surface laid
Geotextiles for
soil erosion control:
Natural products
• Materials
•
•
•
•
•
•
•
•
•
•
•
wood fibre / straw
coir
jute
Others: cotton, wool, paper, sisal,
banana leaves?!
bio- / light degradable
environmentally friendly
organic matter available
nutrients
aesthetics
costs – see later
temporary
other,
3%
jute,
15%
coir,
22%
wood
fibre /
straw,
60%
Geotextiles for
soil erosion control:
Synthetic products
• Materials
• polypropylene, nylon, polyester, polyamide, polyethylene
• permanent
• resist acids, alkalis, microbiological activity
• may interact with vegetation to provide composite methods of soil erosion
control (synergy?)
• aesthetics
• costs – see later
• chemical lobby on Standards Committees
Geotextiles for
soil erosion control
• Surface laid products
• simulate canopy and stem effects of vegetation
• protect against surface erosion processes by
• intercepting rainfall
• storing rainfall
• imparting roughness to flow
• reducing flow velocity
– infiltration
– reduced detachment and transport capacity of flow
Geotextiles for
soil erosion control
• Buried products
• simulate root effect
• additional tensile strength added to soil matrix
• encourages infiltration through the loose, unconsolidated backfill
Geotextiles for
soil erosion control
Product name
Material Characteristics
Weight
Type
(g m-2)
Area of
geotextile
(%)
Buried /
Surface
installation
1
Enkamat (Surface)
3D nylon mesh
265
60
Geomat
S
2
Enkamat (Buried)
3D nylon mesh
265
60
Geomat
B
3
Geojute
100% jute woven mesh
500
54
Bionet
S
4
Bachbettgewebe
100% coir woven mesh
700
58
Bionet
S
5
Fine geojute
100% jute woven mesh (fine)
292
80
Bionet
S
6
Enviromat
Wood chips in a photodegradable
synthetic mesh
450
94
Biomat
S
7
Tensarmat
3D Polypropylene mat
450
38
Geomat
B
Geotextile costs
installation
time
(hrs/ha) *
$’000 / ha**
$ / m2**
min
max
min
max
jute woven
38
1.48
1.73
14.8
17.3
straw blanket
38
1.98
2.59
19.8
25.9
coconut fibre blanket
38
3.2
3.5
32.0
35.0
coconut fibre mesh
38
7.4
8.2
74.0
82.0
straw/coconut fibre blanket
38
2.5
3
25.0
30.0
wood fibre blanket
38
1.98
2.59
19.8
25.9
curled wood fibre blanket
38
1.98
2.59
19.8
25.9
biodegradable fibres with
synthetic netting
38
7.4
8.9
74.0
89.0
synthetic fibre with synthetic
netting
96
8.4
9.9
84.0
99.0
bonded synthetic fibres
96
11.1
13.6
111.0
135.00
*assumes a 2 person crew. **cost data from Caltrans Erosion Control Manual (Draft), Training materials
2003)
Global markets for
erosion control
geotextiles
natural erosion control
products*
synthetic erosion
control products
total erosion control
product market
Region
Consumption
(Mm²)
(%)
Consumption
(Mm²)
(%)
Consumption
(Mm²)
(%)
North America
57
66
44
51
101
58
Western
Europe
17
20
35
40
52
30
World residual
Totals
12
86
14
100
8
87
9
100
20
173
12
100
Annual growth rate estimated at 8.5%
Legislative context driving the
expansion of geotextile
markets in Europe
• Water Framework Directive
• ‘good ecological status’
• Draft Soil Framework Directive
•
•
•
•
Erosion is a “major threat to soil resources
Areas at risk
Risk reduction targets
Incentives / fines
• Sustainable Urban Drainage (SUDs)
Geotextiles for
soil erosion control
• Evaluating geotextiles for erosion control
• How do these products work?
Geotextiles for
soil erosion control
High rainfall intensity, Clay as % of control
High rainfall intensity, Sand as % of control
Low rainfall intensity, Clay as % of control
Low rainfall intensity, Sand as % of control
160
Soil loss as % of control
140
120
100
80
60
40
20
0
control
34
geojute
fine geojute enviramat
natural fibre products
bachbett
enkamat s enkamat b tensarmat
synthetic products
6.Correlation
Validation
of between
resultsgeotextile properties and erosion control effectiveness
coefficients
(soil loss; as measured when rainfall and runoff processes are combined)
Correlation with erosion
control effectiveness
Significance of
correlation
Area of geotextile (%)
-0.8723
p<0.05
Depth of flow (mm)
-0.8302
p<0.05
-0.7095
p<0.05
Water holding capacity (%)
-0.8369
p<0.05
Weight (g m-2)
-0.7189
p<0.05
Wet weight as % after 24 hours
-0.8419
p<0.05
Wet weight as % after 48 hours
-0.5990
p<0.10
Cost ($ m-2)
0.2970
NS
Flow velocity (m s-1)
-0.0681
NS
Mean yarn diameter (mm)
-0.4667
NS
Tensile strength (kN m-1)
0.2939
NS
Thickness (mm)
0.3730
NS
Geotextile property
Manning’s roughness coefficient (n) /
Geotextile Induced Roughness
Source: Rickson, 2000
35
Geotextiles for
soil erosion control
• This work has also identified the salient properties of erosion control geotextiles:
• % cover
• water holding capacity
• geotextile induced roughness
• % weight when wet
• depth of flow ponded
• Can be used by designers and manufacturers to make more effective products
• Can help specifiers / contractors select most effective products
Geotextiles for
soil erosion control
• As well as control of erosion, geotextiles can be used to enhance
vegetation establishment and growth. This is achieved by:
• Control of erosion (of soil + seeds, fertilisers and seedlings)
• Modifying site microclimatic conditions
• Temperature
• Moisture content
• Light interception
• Improving soil properties
• Nutrients
• Organic matter (5 t/ha - jute?? - do we need less top soil then?)
• Soil structure
Case study: Cobrey
Farms, Herefordshire
Case study: Cobrey
Farms
Images c/o Dr Rob Simmons, NSRI
Grassed waterway specifications with and without a geotextile lining (Manning equation)
Without a geotextile lining
Water
Slope
Depth*
way
o
()
(m)
Section
1
5.06
0.049
2
5.06
0.049
3
3.92
0.059
4
2.51
0.083
Total
*plus 20% freeboard.
Width (m)
11.8
29.1
38.2
62.5
Area
2
(m )
224
873
2032
4180
7309
With a geotextile lining
Depth* (m)
Width
(m)
Area
2
(m )
0.08
0.08
0.097
0.136
5.23
12.8
16.8
27.5
116
384
893
1839
3232
Geotextiles for
soil erosion control
• The use of geotextiles in erosion control and slope stabilisation
 Immediate erosion control
 Long term synergistic effects with establishing vegetation
 Use of sustainable resources
 Use of biodegradable, environmentally friendly products
 May contribute organic matter, C, nutrients
 May encourage microbiological activity in the soil
 Increasing data base on geotextile effectiveness in controlling
sediment
 Site aesthetics
Relevance to markets?
Technical performance
alone is not enough…..
• Sustainability procurement by end users / specifiers
• Public and private agencies:
• Governments
• Highway Agencies
• Civil engineering contractors
• Supermarkets
• Agricultural producers
• Impacts on ecosystem goods and services (Millennium Development Goals)
• Environmental Impact Assessments throughout the supply chain
Relevance to markets?
Technical performance alone is not
enough…..
Environmental Impact Statement for the application of jute geotextiles
Area of
impact
Description of
impact
Geographical level
of issue
importance*
I
Human
Beings
e.g. farmer
livelihoods
Flora &
fauna
e.g. impact of jute
production on fauna
Soil &
Geology
e.g. control of soil
loss
Water
e.g. reduction in
sedimentation and
flooding risks
N
R
D
Impact
Nature**
L
*I = International; N = National; R = Regional; D = District; L = Local
**ST = short term; LT = long term; R = Reversible; IR = Irreversible
Significance
Mitigation
measures
6. Conclusions
• Geotextiles are effective at controlling soil erosion and establishing
vegetation
• Understanding geotextile properties is critical (including chemical
properties?)
• Laboratory trials need more field validation
• Effect of changing weather patterns?
• Technical performance alone is not enough
• Demand for erosion control geotextiles is likely to expand
Concluding thought…..
“The nation that destroys its soil destroys itself”
Franklin D Roosevelt
Thank you for your attention
Any questions?