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Tree row and grass strip to sustain filtering and productive function of the riparian zone [Kenya]

technologies_1559 - Kenya

Completeness: 78%

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:
SLM specialist:

Muthoni Mary Njagy

0727 906 945

Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
CDE Centre for Development and Environment (CDE Centre for Development and Environment) - Switzerland

1.3 Conditions regarding the use of data documented through WOCAT

When were the data compiled (in the field)?


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


2. Description of the SLM Technology

2.1 Short description of the Technology

Definition of the Technology:

Tree line with adjacent grass strips as example of a productive and protective riparian area at Kapingazi River

2.2 Detailed description of the Technology


On the south-eastern slopes of Mt. Kenya, the conditions are ideal for agricultural activities. There is plenty of rainfall (2100 mm/year) which is usually reliable. However in the year 2000, the river Kapingazi dried up for the first time since many decades during a dry spell. This led to community activities that finally came up with a system of vegetative interventions to strengthen the riparian zones. The intervention consists of tree planting and establishment of grass strips along the river. Napier grass is planted to stabilize steep slopes and to supply material for the construction of tea baskets.

Purpose of the Technology: The goals of this technology are manifold. Firstly, the vegetation prevents surface water and eroded soil flowing from the agricultural fields directly into the river. Therefore, sediments and chemicals used on the field are retained in the riparian soils and do not pollute the river. Surface water flow from runoff during heavy storms is slowed down and infiltration on soils covered by grass and trees is increased. As a result more groundwater is recharged during the wet seasons, which can be released during the dry season. Thus peak or flood flows are reduced and low flows are improved. Damage during flood flows on the riverbank (through erosion and destabilizing the riparian vegetation) as well as damages of floods downstream can be reduced or avoided.

Establishment / maintenance activities and inputs: Before planting the indigenous trees, water guzzlers like eucalyptus trees were cut down. Indigenous seedlings were planted right along the river at a distance of 2m. Between the trees and the tea plantation a grass strip of up to 10m is established. Some trees were planted scattered on the grass strip. The young trees are surrounded by grasses which are cut regularly every 2 weeks. This reduces competition and enhances growth of the trees. As soon as the trees are big enough, they function as a source of firewood, they can be pruned every 5 months.

Natural / human environment: The studied plot is situated right below the natural mountain forest of Mt. Kenya at the south-eastern slope. The source of Kapingazi River can be found at 1.5 km of walking distance upslope of the plot. Agricultural circumstances are good because of the fertile, volcanic plots and the abundant precipitations. However, the terrain is quite steep.
The zone which is used for tea production reaches from an elevation of 1700 m.a.s.l to 2000 m.a.s.l. Most tea farmers own between 4 and 20 acres. The area of the riparian zone covers 6 m from the river edge and belongs to the government. Since the harvest of the tea leaves requires a high labour input, local workers are hired. Most of the harvest is done during the rainy season because the tea plants are growing fast in this period. For the tea production only the youngest leaves are used, transported in a basket on the worker’s back to the tea factory in the evening.

2.3 Photos of the Technology

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



Region/ State/ Province:

Kenya/Eastern Province

Further specification of location:


2.6 Date of implementation

If precise year is not known, indicate approximate date:
  • less than 10 years ago (recently)

2.7 Introduction of the Technology

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

In the year 2002 the new constitution obliged the government to take care of the water resources. The instrument for this were the WRUA (Water Resource Users Associations), local initiatives of land users that promote protective measures along the rivers.

3. Classification of the SLM Technology

3.1 Main purpose(s) of the Technology

  • reduce, prevent, restore land degradation

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



  • Perennial (non-woody) cropping
Main crops (cash and food crops):

major cash crop: Tea


Major land use problems (compiler’s opinion): The main land use problems are pollution of the riverwater, low rainwater storage that provokes floods, too few water during the dry season and riverbank erosion.

Major land use problems (land users’ perception): The main problem is the few water in the dry season that prevents irrigation.

Type of cropping system and major crops comments: Additionally, few food crops are planted in a relatively small homegarden.

3.3 Further information about land use

Number of growing seasons per year:
  • 2

Longest growing period in days: 60 Longest growing period from month to month: april to may Second longest growing period in days: 60 Second longest growing period from month to month: november to december

3.4 SLM group to which the Technology belongs

  • improved ground/ vegetation cover

3.5 Spread of the Technology

Specify the spread of the Technology:
  • evenly spread over an area
If the Technology is evenly spread over an area, indicate approximate area covered:
  • < 0.1 km2 (10 ha)

Since the technology is only used by one farmer at a single spot, it does not make sense to indicate the area. Furthermore, the length along the river is more important than the area.

3.6 SLM measures comprising the Technology

vegetative measures

vegetative measures

  • V1: Tree and shrub cover
  • V2: Grasses and perennial herbaceous plants

Main measures: vegetative measures

Type of vegetative measures: aligned: -along boundary, scattered / dispersed

3.7 Main types of land degradation addressed by the Technology

biological degradation

biological degradation

  • Bs: quality and species composition/ diversity decline
water degradation

water degradation

  • Hs: change in quantity of surface water
  • Hp: decline of surface water quality
  • Hw: reduction of the buffering capacity of wetland areas

Main type of degradation addressed: Hp: decline of surface water quality, Hw: reduction of the buffering capacity of wetland areas

Secondary types of degradation addressed: Bs: quality and species composition /diversity decline, Hs: change in quantity of surface water

Main causes of degradation: deforestation / removal of natural vegetation (incl. forest fires) (Riparian trees were chopped down.), education, access to knowledge and support services (People didn't know about the consequences of the deforestation.), planting directly next to river

3.8 Prevention, reduction, or restoration of land degradation

Specify the goal of the Technology with regard to land degradation:
  • prevent land degradation
  • reduce land degradation

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

4.1 Technical drawing of the Technology


Manuel Fischer

4.2 Technical specifications/ explanations of technical drawing

The area between the river and the tea plantation is used to establish a riparian habitat. Trees are planted along the river and also on the adjacent grazing land. The grass is cut regularly and used as fodder. A bee hive was installed to generate additional income.

Location: Manyatta. Embu / Eastern Province

Date: 28.12.2013

Technical knowledge required for field staff / advisors: low

Technical knowledge required for land users: low

Main technical functions: improvement of ground cover, increase of infiltration, sediment retention / trapping, sediment harvesting

Secondary technical functions: promotion of vegetation species and varieties (quality, eg palatable fodder)

Aligned: -along boundary
Vegetative material: T : trees / shrubs
Number of plants per (ha): 30
Vertical interval within rows / strips / blocks (m): 3

Scattered / dispersed
Vegetative material: G : grass

Trees/ shrubs species: indigenous trees, Napier grass

Grass species: normal grass

4.3 General information regarding the calculation of inputs and costs

Specify currency used for cost calculations:
  • US Dollars
Indicate average wage cost of hired labour per day:


4.4 Establishment activities

Activity Type of measure Timing
1. Tree planting Vegetative During rainy season
2. Replanting of seedlings which dried up Vegetative
3. Planting trees Management At the beginning of the rainy season

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 Tree planting during rain season Persons/day 6.0 3.3333333 20.0 100.0
Labour Replanting of seedlings Persons/day 2.0 3.333333 6.67 100.0
Labour Planting trees before rain season Persons/day 8.0 3.333333 26.67 100.0
Plant material Seedlings pieces 70.0 0.111 7.77
Plant material Seedlings for replanting pieces 20.0 0.111 2.22 100.0
Plant material Riparian seedlings pieces 90.0 0.034555 3.11 100.0
Total costs for establishment of the Technology 66.44

Duration of establishment phase: 1 month(s)

4.6 Maintenance/ recurrent activities

Activity Type of measure Timing/ frequency
1. Weeding the area around the trees to get fodder and boost the tree growth Vegetative every 2 weeks for 4 years
2. Weeding the lawns for better growth of the trees and for fodder Management every 2 weeks during raining season

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 Weeding the area around the trees Persons/day 16.0 3.33333 53.33 100.0
Labour Weeding the lawns Persons/day 64.0 3.33333 213.33 100.0
Total costs for maintenance of the Technology 266.66

Machinery/ tools: Jembe (Machete)

The costs were calculated for a riparian area with a length of 100m and a width of 10m, since hectares are difficult to apply on a riparian context. The determinant factor for the costs is labour. In this case, the costs are very low because the trees were only planted every 10 metres along the riparian. The seedlings have to be bought in a nursery. Most of the bushes regrow naturally and do not need any management.
Some of the seedlings had to be replanted, because they dried up. The required equipment like a spade is available on nearly every farm or can be borrowed from neighbours and is thus not added to the costs.

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:


Specifications/ comments on rainfall:

Most of the rain falls during the rainy seasons from April-May and Oct-Nov.

Agro-climatic zone
  • sub-humid

Thermal climate class: subtropics.,Kenia

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%)
  • 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.

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)
Topsoil organic matter:
  • medium (1-3%)
If available, attach full soil description or specify the available information, e.g. soil type, soil PH/ acidity, Cation Exchange Capacity, nitrogen, salinity etc.

Soil fertility is medium

Soil drainage / infiltration is good

Soil water storage capacity is very high

5.4 Water availability and quality

Ground water table:

< 5 m

Availability of surface water:


Water quality (untreated):

good drinking water

Comments and further specifications on water quality and quantity:

Availability of surface water: Also excess and poor/none

5.5 Biodiversity

Species diversity:
  • medium

5.6 Characteristics of land users applying the Technology

Market orientation of production system:
  • mixed (subsistence/ commercial
  • commercial/ market
Off-farm income:
  • > 50% of all income
Relative level of wealth:
  • rich
Individuals or groups:
  • employee (company, government)
Level of mechanization:
  • manual work
  • women
  • men
Indicate other relevant characteristics of the land users:

Land users applying the Technology are mainly Leaders / privileged

Population density: > 500 persons/km2

Off-farm income specification: Owner is a member of the parliament.

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

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

Land ownership:
  • individual, not titled
Land use rights:
  • individual
Water use rights:
  • individual

Land user was a former member of parliament

5.9 Access to services and infrastructure

  • poor
  • moderate
  • good
  • poor
  • moderate
  • good
technical assistance:
  • poor
  • moderate
  • good
employment (e.g. off-farm):
  • poor
  • moderate
  • good
  • poor
  • moderate
  • good
  • 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


crop production


fodder production


wood production

Comments/ specify:

Pruning of trees

Income and costs

farm income

Other socio-economic impacts

Grass for basket production.


Comments/ specify:

Pruning the trees

Socio-cultural impacts

cultural opportunities

Comments/ specify:


SLM/ land degradation knowledge


Livelihood and human well-being

Comments/ specify:

Through the increase of the water quality, the technology improves the access to clean water.

Ecological impacts

Water cycle/ runoff

water quantity


water quality


harvesting/ collection of water


surface runoff


soil moisture


soil cover

Biodiversity: vegetation, animals

plant diversity


animal diversity


habitat diversity


6.2 Off-site impacts the Technology has shown

reliable and stable stream flows in dry season


downstream siltation


groundwater/ river pollution


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

Climate-related extremes (disasters)

Meteorological disasters
How does the Technology cope with it?
local rainstorm well
local windstorm well
Climatological disasters
How does the Technology cope with it?
drought not known
Hydrological disasters
How does the Technology cope with it?
general (river) flood not well

Other climate-related consequences

Other climate-related consequences
How does the Technology cope with it?
reduced growing period 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:


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

  • 1-10%
If available, quantify (no. of households and/ or area covered):

10% of all the riparian land users have adopted the technology

Of all those who have adopted the Technology, how many have did so spontaneously, i.e. without receiving any material incentives/ payments?
  • 10-50%

70% of land user families have adopted the Technology with external material support

Comments on acceptance with external material support: 10% of all the riparian land users have adopted the technology. The external support was the provision of seedlings.

30% of land user families have adopted the Technology without any external material support

There is a moderate trend towards spontaneous adoption of the Technology

Comments on adoption trend: Through the action of several organisations, the attention of the land users is drawn to a proper riparian management.

6.7 Strengths/ advantages/ opportunities of the Technology

Strengths/ advantages/ opportunities in the land user’s view
The river does not dry up easily during dry seasons. The grass yield can be used for fodder purposes.

How can they be sustained / enhanced? disseminating the knowledge among the farmers.
Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view
A vivid and stable riparian ecosystem is the key to ensure biodiversity and stability of the riverbanks. This leads to a smaller vulnerability to floods or droughts and combats degradation.

How can they be sustained / enhanced? continuous awareness raising among the land users.

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

Weaknesses/ disadvantages/ risks in the compiler’s or other key resource person’s view How can they be overcome?
Labour input for weeding is high cutting grass at a bigger height

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