Technologies

Reshaping of gully erosion through integration of silt fences, erosion blankets and brush packing [South Africa]

Reshaping of gullies

technologies_3359 - South Africa

Completeness: 92%

1. General information

1.2 Contact details of resource persons and institutions involved in the assessment and documentation of the Technology

Key resource person(s)

SLM specialist:

Buckle Jacob

+27828207083

JBuckle@environment.gov.za

Department of Environmental Affairs - South Africa

14 Loop Street, Cape Town, South Africa, 8000

South Africa

Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)
Working on Ecosystems (Natural Resource Management Programmes – DEA, South Africa)
Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
SMC Synergy (SMC Synergy) - South Africa

1.3 Conditions regarding the use of data documented through WOCAT

When were the data compiled (in the field)?

17/01/2018

The compiler and key resource person(s) accept the conditions regarding the use of data documented through WOCAT:

Yes

1.4 Declaration on sustainability of the described Technology

Is the Technology described here problematic with regard to land degradation, so that it cannot be declared a sustainable land management technology?

No

1.5 Reference to Questionnaire(s) on SLM Approaches

Working for Water
approaches

Working for Water [South Africa]

Government funded restoration/rehabilitation initiative as part of Working for Water project. Aim was to eradicate alien invasive.

  • Compiler: Klaus Kellner

2. Description of the SLM Technology

2.1 Short description of the Technology

Definition of the Technology:

The rehabilitation of active gully erosion by re-sloping the banks of the gully in an effort to manage the energy of the water entering the system. Bare soil is protected from erosion by covering it with erosion blankets, brush packing and the establishment of silt fences.

2.2 Detailed description of the Technology

Description:

This gully reshaping project was conducted in the Mapungubwe National Park in the Limpopo Province of South Africa. The area receives summer rainfall with an annual average of around 600 to 700 mm. Thunderstorms are common. Due to overgrazing on highly erodible soils, gully headcuts are actively migrating upstream. The reshaping technology can be considered for any gully of up to 2 meters in depth (even on duplex - highly erodible soils - gypsum must, however, be added to the relocated topsoil in this case). The purpose of re-sloping is to reduce the gradient of gully heads and sidewalls, thereby reducing the energy of runoff water. This also leads to enhanced vegetation cover and reduced sediment transport in the gully. Resloping of gullies is performed in stages:
Stage One: Remove all viable and useful plants in and around the active gully system that will be affected by the reshaping – store these for replanting.
Stage Two: Relocate the usable topsoil to the edge of the gully reshape footprint.
Stage Three: Reshaping of the gully banks to a 1:3 slope (relative to the new valley floor level after refilling with bank material - see figure). Start by removing the top of the bank and placing it on the gully floor. Make sure to compact the soil from the banks - breaking up clods to smaller particles. Continue to remove more of the bank material and compact it in layers to form a disk shape profile (cross section - see sketch).
Stage Four: Spread the topsoil evenly over the newly created gentle sloping profile. Add indigenous grass seed (if available: if not, exotic grasses).
Stage Five: Construct silt fences (made of fabric filter cloth - Geotextile) above the water entry points and inside the newly formed profile (around 10 m apart).
Stage Six: Cover the area with soil erosion blankets (bio-jute) and/or mulch and/or brush packing with thorny local woody biomass.
Stage Seven: Replant recovered plants - protect the area with fences if possible until grass cover established.

2.3 Photos of the Technology

2.5 Country/ region/ locations where the Technology has been applied and which are covered by this assessment

Country:

South Africa

Region/ State/ Province:

Limpopo province

Further specification of location:

Mapungubwe National Park

2.6 Date of implementation

Indicate year of implementation:

2017

2.7 Introduction of the Technology

Specify how the Technology was introduced:
  • through projects/ external interventions
Comments (type of project, etc.):

Working on Ecosystem Services

3. Classification of the SLM Technology

3.1 Main purpose(s) of the Technology

  • reduce, prevent, restore land degradation
  • conserve ecosystem
  • protect a watershed/ downstream areas – in combination with other Technologies
  • reduce risk of disasters
  • create beneficial social impact

3.2 Current land use type(s) where the Technology is applied

Grazing land

Grazing land

Extensive grazing land:
  • Ranching
Waterways, waterbodies, wetlands

Waterways, waterbodies, wetlands

  • Drainage lines, waterways
  • Swamps, wetlands
Main products/ services:

Sediment trap, alluvial flood plain

3.3 Further information about land use

Water supply for the land on which the Technology is applied:
  • rainfed
Number of growing seasons per year:
  • 1
Specify:

Summer rainfall - October to April

Livestock density (if relevant):

High - game (various species)

3.4 SLM group to which the Technology belongs

  • improved ground/ vegetation cover
  • cross-slope measure
  • surface water management (spring, river, lakes, sea)

3.5 Spread of the Technology

Specify the spread of the Technology:
  • applied at specific points/ concentrated on a small area

3.6 SLM measures comprising the Technology

structural measures

structural measures

  • S6: Walls, barriers, palisades, fences
management measures

management measures

  • M3: Layout according to natural and human environment

3.7 Main types of land degradation addressed by the Technology

soil erosion by water

soil erosion by water

  • Wg: gully erosion/ gullying
  • Wo: offsite degradation effects
water degradation

water degradation

  • Hp: decline of surface water quality
  • Hw: reduction of the buffering capacity of wetland areas

3.8 Prevention, reduction, or restoration of land degradation

Specify the goal of the Technology with regard to land degradation:
  • reduce land degradation
  • restore/ rehabilitate severely degraded land

4. Technical specifications, implementation activities, inputs, and costs

4.1 Technical drawing of the Technology

Author:

J Buckle

Date:

17/01/2018

Author:

J Buckle

Date:

17/01/2018

4.2 Technical specifications/ explanations of technical drawing

Rehabilitation of gully erosion - 0.5 m to 2 m deep.
Reslope gully banks from vertical to an approximately 30-degree slope.
Silt fences are established above gull head-cut - silt fences inside the reshaped gully - in the region of 10 m apart.
Brush packing with thorny biomass to prevent grazing and provide a micro-climate for grass seed to germinate and establish.
Silt fences are temporary sediment control devices used on rehabilitation sites to reduce sediment movement downhill. A typical fence consists of a piece of synthetic filter fabric (also called a geotextile) stretched between a series of wooden or metal fence stakes along a horizontal contour level.

4.3 General information regarding the calculation of inputs and costs

Specify how costs and inputs were calculated:
  • per Technology area
Indicate size and area unit:

0.017 ha

Indicate exchange rate from USD to local currency (if relevant): 1 USD =:

12.0

Indicate average wage cost of hired labour per day:

R140/day

4.4 Establishment activities

Activity Type of measure Timing
1. Remove plants Vegetative 2 to 3 months before the summer rain
2. Remove topsoil Structural 2 to 3 months before the summer rain
3. Reshaping, compacting, layering Structural 2 to 3 months before the summer rain
4. Reseeding Vegetative 2 to 3 months before the summer rain
5. Soil erosion blankets installation Structural 2 to 3 months before the summer rain
6. Silt fences Structural 2 to 3 months before the summer rain
7. Brush packing Structural 2 to 3 months before the summer rain

4.5 Costs and inputs needed for establishment

Specify input Unit Quantity Costs per Unit Total costs per input % of costs borne by land users
Labour Unskilled labour (including transport) per day 60.0 240.0 14400.0
Equipment Picks, spades, hand compactor, pliers, hopper, bow saws, hammer, wheel barrow (renting the equipment) per day 35.0 20.0 700.0
Plant material Grass seed mix per kilogram 2.0 75.0 150.0
Construction material Erosion blankets per square meter 170.0 15.0 2550.0
Construction material Silt fences per meter 16.0 15.0 240.0
Total costs for establishment of the Technology 18040.0
If land user bore less than 100% of costs, indicate who covered the remaining costs:

Department of Environmental Affairs - NRM programmes

4.6 Maintenance/ recurrent activities

Activity Type of measure Timing/ frequency
1. After floods restore site (silt fences and brush packing) Structural After floods

4.7 Costs and inputs needed for maintenance/ recurrent activities (per year)

Specify input Unit Quantity Costs per Unit Total costs per input % of costs borne by land users
Labour Restoration of site after flooding events per day 6.0 240.0 1440.0
Equipment Tools to restore fences and brush packing per day 3.0 20.0 60.0
Construction material Silt fences per day 10.0 15.0 150.0
Total costs for maintenance of the Technology 1650.0
If land user bore less than 100% of costs, indicate who covered the remaining costs:

Department of Environmental Affairs - NRM programmes

4.8 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

Labour availability, soil hardness, availability of material, transport cost

5. Natural and human environment

5.1 Climate

Annual rainfall
  • < 250 mm
  • 251-500 mm
  • 501-750 mm
  • 751-1,000 mm
  • 1,001-1,500 mm
  • 1,501-2,000 mm
  • 2,001-3,000 mm
  • 3,001-4,000 mm
  • > 4,000 mm
Specify average annual rainfall (if known), in mm:

650.00

Specifications/ comments on rainfall:

Summer thunderstorms

Agro-climatic zone
  • semi-arid

Hot summers and dry winters

5.2 Topography

Slopes on average:
  • flat (0-2%)
  • gentle (3-5%)
  • moderate (6-10%)
  • rolling (11-15%)
  • hilly (16-30%)
  • steep (31-60%)
  • very steep (>60%)
Landforms:
  • plateau/plains
  • ridges
  • mountain slopes
  • hill slopes
  • footslopes
  • valley floors
Altitudinal zone:
  • 0-100 m a.s.l.
  • 101-500 m a.s.l.
  • 501-1,000 m a.s.l.
  • 1,001-1,500 m a.s.l.
  • 1,501-2,000 m a.s.l.
  • 2,001-2,500 m a.s.l.
  • 2,501-3,000 m a.s.l.
  • 3,001-4,000 m a.s.l.
  • > 4,000 m a.s.l.
Indicate if the Technology is specifically applied in:
  • concave situations
Comments and further specifications on topography:

Flood plane

5.3 Soils

Soil depth on average:
  • very shallow (0-20 cm)
  • shallow (21-50 cm)
  • moderately deep (51-80 cm)
  • deep (81-120 cm)
  • very deep (> 120 cm)
Soil texture (topsoil):
  • medium (loamy, silty)
Soil texture (> 20 cm below surface):
  • fine/ heavy (clay)
Topsoil organic matter:
  • high (>3%)

5.4 Water availability and quality

Ground water table:

< 5 m

Availability of surface water:

medium

Water quality (untreated):

unusable

Is water salinity a problem?

Yes

Is flooding of the area occurring?

Yes

Regularity:

episodically

5.5 Biodiversity

Species diversity:
  • high
Habitat diversity:
  • low

5.6 Characteristics of land users applying the Technology

other (specify):

Protected area

Market orientation of production system:
  • mixed (subsistence/ commercial
Off-farm income:
  • less than 10% of all income
Relative level of wealth:
  • poor
Individuals or groups:
  • employee (company, government)
Level of mechanization:
  • manual work
Gender:
  • women
  • men
Age of land users:
  • middle-aged
Indicate other relevant characteristics of the land users:

People are brought into the protected areas to work on the rehabilitation projects.

5.7 Average area of land owned or leased by land users applying the Technology

  • < 0.5 ha
  • 0.5-1 ha
  • 1-2 ha
  • 2-5 ha
  • 5-15 ha
  • 15-50 ha
  • 50-100 ha
  • 100-500 ha
  • 500-1,000 ha
  • 1,000-10,000 ha
  • > 10,000 ha
Is this considered small-, medium- or large-scale (referring to local context)?
  • medium-scale
Comments:

National park

5.8 Land ownership, land use rights, and water use rights

Land ownership:
  • state
Land use rights:
  • communal (organized)
  • State
  • Government land

5.9 Access to services and infrastructure

health:
  • poor
  • moderate
  • good
education:
  • poor
  • moderate
  • good
technical assistance:
  • poor
  • moderate
  • good
employment (e.g. off-farm):
  • poor
  • moderate
  • good
markets:
  • poor
  • moderate
  • good
energy:
  • poor
  • moderate
  • good
roads and transport:
  • poor
  • moderate
  • good
drinking water and sanitation:
  • poor
  • moderate
  • good
financial services:
  • poor
  • moderate
  • good

6. Impacts and concluding statements

6.1 On-site impacts the Technology has shown

Socio-economic impacts

Production

fodder production

decreased
increased
Comments/ specify:

Natural fodder for game

land management

hindered
simplified
Comments/ specify:

Habitat for wildlife and plants improve

Water availability and quality

water availability for livestock

decreased
increased
Comments/ specify:

Improved water quantity for game

water quality for livestock

decreased
increased
Comments/ specify:

Better quality water for game

Income and costs

diversity of income sources

decreased
increased
Comments/ specify:

Improve aesthetic value for tourism

Other socio-economic impacts

Job creation

Comments/ specify:

Job creation for communities outside the protected area

Improved skill levels

Comments/ specify:

Community receive training in rehabilitation methods

Socio-cultural impacts

food security/ self-sufficiency

reduced
improved
Comments/ specify:

Improved income for communities

recreational opportunities

reduced
improved
Comments/ specify:

Aesthetic improvement for tourism

national institutions

weakened
strengthened
Comments/ specify:

Improvement of the protected area for SANPARKS

SLM/ land degradation knowledge

reduced
improved
Comments/ specify:

Training received by communities

Ecological impacts

Water cycle/ runoff

water quantity

decreased
increased

water quality

decreased
increased

surface runoff

increased
decreased
Soil

soil cover

reduced
improved

soil loss

increased
decreased

soil accumulation

decreased
increased

soil crusting/ sealing

increased
reduced

soil organic matter/ below ground C

decreased
increased
Biodiversity: vegetation, animals

Vegetation cover

decreased
increased

biomass/ above ground C

decreased
increased

plant diversity

decreased
increased

habitat diversity

decreased
increased
Climate and disaster risk reduction

flood impacts

increased
decreased

drought impacts

increased
decreased

micro-climate

worsened
improved

6.2 Off-site impacts the Technology has shown

downstream siltation

increased
decreased

buffering/ filtering capacity

reduced
improved
Comments regarding impact assessment:

The accumulative effect of treating all gully head-cut erosion in the floodplain will have an effect on sediment loads in the Limpopo river

6.3 Exposure and sensitivity of the Technology to gradual climate change and climate-related extremes/ disasters (as perceived by land users)

Gradual climate change

Gradual climate change
Season Type of climatic change/ extreme How does the Technology cope with it?
annual temperature increase well
seasonal temperature summer increase well
annual rainfall decrease well
seasonal rainfall summer decrease well

Climate-related extremes (disasters)

Meteorological disasters
How does the Technology cope with it?
local thunderstorm well
Climatological disasters
How does the Technology cope with it?
land fire well
Hydrological disasters
How does the Technology cope with it?
flash flood well

6.4 Cost-benefit analysis

How do the benefits compare with the establishment costs (from land users’ perspective)?
Short-term returns:

slightly negative

Long-term returns:

slightly positive

How do the benefits compare with the maintenance/ recurrent costs (from land users' perspective)?
Short-term returns:

slightly negative

Long-term returns:

slightly positive

6.5 Adoption of the Technology

  • single cases/ experimental
Of all those who have adopted the Technology, how many have did so spontaneously, i.e. without receiving any material incentives/ payments?
  • 0-10%
Comments:

This technology can be adopted only if funds are available from the government.

6.6 Adaptation

Has the Technology been modified recently to adapt to changing conditions?

Yes

If yes, indicate to which changing conditions it was adapted:
  • climatic change/ extremes
Specify adaptation of the Technology (design, material/ species, etc.):

Preventative erosion measures above the intervention.

6.7 Strengths/ advantages/ opportunities of the Technology

Strengths/ advantages/ opportunities in the land user’s view
Good technology to stabilise degraded landscapes
Technology helps to improve the habitat - biodiversity in the protected area
Technology helps to reduce the off-site effects of polluted surface water and sediment accumulation in rivers
Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view
Good technology to stabilise degraded landscapes
Technology helps to improve the habitat - biodiversity in the protected area
Technology helps to reduce the off-site effects of sediment accumulation in rivers

6.8 Weaknesses/ disadvantages/ risks of the Technology and ways of overcoming them

Weaknesses/ disadvantages/ risks in the land user’s view How can they be overcome?
Sensitive to flooding Better timing of intervention
Sensitive to fire Construct fire breaks around interventions

7. References and links

7.1 Methods/ sources of information

  • interviews with SLM specialists/ experts

1

7.2 References to available publications

Title, author, year, ISBN:

Wetland Rehabilitation Guidelines, W Russel, 2009, ISBN 978-1-77005-640-4

Available from where? Costs?

Water Research Commission - South Africa - WRC report TT 341/09

Title, author, year, ISBN:

Practical Techniques for Habitat & Wildlife Management: a guide for game ranches, conservation areas and farmland, Ken Coetzee, 2016,ISBN: 978-0-986-70844-9

Available from where? Costs?

New Voices Publishing

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