Trees stabilizing the riverbank, Napier grass in the back. (Manuel Fischer (Manyatta, Embu))

Productive use of the riparian area using Napier grass and protection of the riverbank with indigenous trees at Kapingazi River (Kenya)

Description

A riparian area that is frequently flooded requires a special treatment because conventional agriculture is not possible. Trees along the riverbank and Napier grass on the remaining space still allow a productive use despite the difficult circumstances.

On the southeastern slopes of Mt. Kenya, the circumstances are ideal for agricultural activities, the rains are plenty and normally reliable. The plot owner started realizing a problem of riverbank degradation 17 years ago. But still he continued the traditional way of agriculture, planting beans and maize. Since his plot is on the slip-off slope only few metres above the river level, it experienced regular floods in case of heavy rainfalls, destroying the plants and leading to crop failures. Conventional plants like maize and beans do not resist such an excess of water. To fight the land loss and the bad harvest, the farmer introduced indigenous trees along the river and Napier fighting the riverbank degradation. Behind that, several rows of the flood resistant Napier grass were planted to still use the area in a productive way.

Purpose of the Technology: Above all, the goal of this technology is to get a high grass production. As a side effect results a quite good protection of the riparian area. The vegetation prevents rainwater from running directly from the fields into the water. Therefore, the chemicals from the field get stuck in the riparian soils and don't pollute the river. In the same way the infiltration in the riparian enlarges the total infiltration since the water would go to the river directly. Especially the raw surface of the riparian allows more infiltration and interception storage of water. This surplus of stored water is able to provide river water for a longer period, when rains are humble for a longer period. In case of floods, the increased infiltration potential can cut the peak flow and thus prevent damages. The grass yield is used as a fodder for the cows.

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 1 m. Behind the tree row, Napier grass is planted and harvested twice a year. The cutting and harvesting of the grass is done regularly such that animals can be provided with fodder every day. As soon as the trees are big enough, they function as a source of fire wood, they can be pruned every 5 months.

Natural / human environment: The studied plot is situated between the tea and the coffee zone at an elevation of 1663 m.a.s.l. This small-scale farm does not produce tea nor coffee, there is mainly subsistence agricultural production and some few products are sold on the market. Rainfall is reliable and ensures a regular production.

Location

Location: Embu, Kenya/Eastern Province, Kenya

No. of Technology sites analysed:

Geo-reference of selected sites
  • 37.47201, -0.42611

Spread of the Technology: evenly spread over an area (0.00075 km²)

In a permanently protected area?:

Date of implementation: 10-50 years ago

Type of introduction
Ground stabilizing Napier grass that is used for fodder. (Manuel Fischer (Manyatta))

Classification of the Technology

Main purpose
  • improve production
  • reduce, prevent, restore land degradation
  • conserve ecosystem
  • protect a watershed/ downstream areas – in combination with other Technologies
  • preserve/ improve biodiversity
  • reduce risk of disasters
  • adapt to climate change/ extremes and its impacts
  • mitigate climate change and its impacts
  • create beneficial economic impact
  • create beneficial social impact
Land use
Land use mixed within the same land unit: Yes - Agro-silvopastoralism

  • Cropland
    • Annual cropping: fodder crops - grasses
    • Tree and shrub cropping
    Number of growing seasons per year: 2
  • Grazing land
    • Cut-and-carry/ zero grazing
  • Forest/ woodlands
Water supply
  • rainfed
  • mixed rainfed-irrigated
  • full irrigation

Purpose related to land degradation
  • prevent land degradation
  • reduce land degradation
  • restore/ rehabilitate severely degraded land
  • adapt to land degradation
  • not applicable
Degradation addressed
  • soil erosion by water - Wt: loss of topsoil/ surface erosion, Wr: riverbank erosion
  • biological degradation - Bs: quality and species composition/ diversity decline
  • water degradation - Hp: decline of surface water quality
SLM group
  • improved plant varieties/ animal breeds
SLM measures
  • vegetative measures - V1: Tree and shrub cover, V2: Grasses and perennial herbaceous plants

Technical drawing

Technical specifications
A tree row is aligned directly beside the riverbed with a spacing of 1m. Directly behind the trees, Napier grass is planted up to a width of 15m. Adjacent to the Napier grass, there is cropland.

Location: Manyatta. Embu West / Eastern Province

Date: 28.12.2013

Technical knowledge required for field staff / advisors: low

Technical knowledge required for land users: low

Main technical functions: stabilisation of soil (eg by tree roots against land slides), improvement of water quality, buffering / filtering water

Secondary technical functions: improvement of ground cover, increase of biomass (quantity)

Aligned: -along boundary
Vegetative material: T : trees / shrubs
Vertical interval within rows / strips / blocks (m): 1

Scattered / dispersed
Vegetative material: G : grass
Spacing between rows / strips / blocks (m): 0.8
Vertical interval within rows / strips / blocks (m): 0.8

Trees/ shrubs species: Grevillea, Mutundu, Miburu, Mulinga, Mugumo

Grass species: Napier Grass

Slope (which determines the spacing indicated above): 0%
Author: Manuel Fischer

Establishment and maintenance: activities, inputs and costs

Calculation of inputs and costs
  • Costs are calculated: per Technology unit
  • Currency used for cost calculation: USD
  • Exchange rate (to USD): 1 USD = n.a
  • Average wage cost of hired labour per day: 3.33
Most important factors affecting the costs
n.a.
Establishment activities
  1. Chopping bad trees (Timing/ frequency: anytime)
  2. Tree planting (Timing/ frequency: rainy season)
  3. Planting of Napier grass (Timing/ frequency: Beginning of rainy season)
Establishment inputs and costs
Specify input Unit Quantity Costs per Unit (USD) Total costs per input (USD) % of costs borne by land users
Labour
Chopping bad trees Persons/day 2.5 3.2 8.0 100.0
Tree planting Persons/day 5.0 3.6 18.0 100.0
Planting of Napier grass Persons/day 2.0 2.75 5.5 100.0
Plant material
Seedling Pieces 70.0 0.114285 8.0 100.0
Total costs for establishment of the Technology 39.5
Total costs for establishment of the Technology in USD 39.5
Maintenance activities
  1. Adding manure (Timing/ frequency: 2 times a month)
  2. Harvest of Napier (Timing/ frequency: 2 times per year after rainy season)
  3. Pruning (Timing/ frequency: None)
Maintenance inputs and costs
Specify input Unit Quantity Costs per Unit (USD) Total costs per input (USD) % of costs borne by land users
Labour
Adding manure Persons/day 0.2 2.25 0.45 100.0
Harvest of Napier Persons/day 2.0 3.3333 6.67 100.0
Prunning Persons/day 2.0 3.25 6.5 100.0
Total costs for maintenance of the Technology 13.62
Total costs for maintenance of the Technology in USD 13.62

Natural environment

Average 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
Agro-climatic zone
  • humid
  • sub-humid
  • semi-arid
  • arid
Specifications on climate
Average annual rainfall in mm: 1703.0
Name of the meteorological station: source: http://www.wri.org/publication/content/9291
Thermal climate class: tropics. http://www.levoyageur.net/weather-city-EMBU.html
Slope
  • 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
Altitude
  • 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.
Technology is applied in
  • convex situations
  • concave situations
  • not relevant
Soil depth
  • 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)
  • coarse/ light (sandy)
  • medium (loamy, silty)
  • fine/ heavy (clay)
Soil texture (> 20 cm below surface)
  • coarse/ light (sandy)
  • medium (loamy, silty)
  • fine/ heavy (clay)
Topsoil organic matter content
  • high (>3%)
  • medium (1-3%)
  • low (<1%)
Groundwater table
  • on surface
  • < 5 m
  • 5-50 m
  • > 50 m
Availability of surface water
  • excess
  • good
  • medium
  • poor/ none
Water quality (untreated)
  • good drinking water
  • poor drinking water (treatment required)
  • for agricultural use only (irrigation)
  • unusable
Water quality refers to:
Is salinity a problem?
  • Yes
  • No

Occurrence of flooding
  • Yes
  • No
Species diversity
  • high
  • medium
  • low
Habitat diversity
  • high
  • medium
  • low

Characteristics of land users applying the Technology

Market orientation
  • subsistence (self-supply)
  • mixed (subsistence/ commercial)
  • commercial/ market
Off-farm income
  • less than 10% of all income
  • 10-50% of all income
  • > 50% of all income
Relative level of wealth
  • very poor
  • poor
  • average
  • rich
  • very rich
Level of mechanization
  • manual work
  • animal traction
  • mechanized/ motorized
Sedentary or nomadic
  • Sedentary
  • Semi-nomadic
  • Nomadic
Individuals or groups
  • individual/ household
  • groups/ community
  • cooperative
  • employee (company, government)
Gender
  • women
  • men
Age
  • children
  • youth
  • middle-aged
  • elderly
Area used per household
  • < 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
Scale
  • small-scale
  • medium-scale
  • large-scale
Land ownership
  • state
  • company
  • communal/ village
  • group
  • individual, not titled
  • individual, titled
Land use rights
  • open access (unorganized)
  • communal (organized)
  • leased
  • individual
Water use rights
  • open access (unorganized)
  • communal (organized)
  • leased
  • individual
Access to services and infrastructure
health

poor
x
good
education

poor
x
good
technical assistance

poor
x
good
employment (e.g. off-farm)

poor
x
good
markets

poor
x
good
energy

poor
x
good
roads and transport

poor
x
good
drinking water and sanitation

poor
x
good
financial services

poor
x
good

Impacts

Socio-economic impacts
Crop production
decreased
x
increased

fodder production
decreased
x
increased

animal production
decreased
x
increased

risk of production failure
increased
x
decreased

diversity of income sources
decreased
x
increased

Fuelwood production through pruning
decreased
x
increased

Socio-cultural impacts
food security/ self-sufficiency
reduced
x
improved

SLM/ land degradation knowledge
reduced
x
improved

Ecological impacts
water quality
decreased
x
increased

soil cover
reduced
x
improved

plant diversity
decreased
x
increased

habitat diversity
decreased
x
increased

Stabilization of riverbank
reduced
x
improved

Infiltration
decreased
x
increased

Off-site impacts
reliable and stable stream flows in dry season (incl. low flows)
reduced
x
increased

downstream siltation
increased
x
decreased

groundwater/ river pollution
increased
x
reduced

Cost-benefit analysis

Benefits compared with establishment costs
Short-term returns
very negative
x
very positive

Long-term returns
very negative
x
very positive

Benefits compared with maintenance costs
Short-term returns
very negative
x
very positive

Long-term returns
very negative
x
very positive

Establishment and maintenance costs are quite low.

Climate change

Gradual climate change
annual temperature increase

not well at all
x
very well
Climate-related extremes (disasters)
local rainstorm

not well at all
x
very well
local windstorm

not well at all
x
very well
drought

not well at all
x
very well
general (river) flood

not well at all
x
very well
Other climate-related consequences
reduced growing period

not well at all
x
very well

Adoption and adaptation

Percentage of land users in the area who have adopted the Technology
  • single cases/ experimental
  • 1-10%
  • 11-50%
  • > 50%
Of all those who have adopted the Technology, how many have done so without receiving material incentives?
  • 0-10%
  • 11-50%
  • 51-90%
  • 91-100%
Has the Technology been modified recently to adapt to changing conditions?
  • Yes
  • No
To which changing conditions?
  • climatic change/ extremes
  • changing markets
  • labour availability (e.g. due to migration)

Conclusions and lessons learnt

Strengths: land user's view
  • Protection of the riverbank and reduced riverbank erosion.

    How can they be sustained / enhanced? Regular management of riparian trees by replacing dead trees with new ones.
  • Productive function of the Napier grass in terms of fodder and of the trees in terms of pruning for fire wood.

    How can they be sustained / enhanced? Careful use of the trees and the grass enables a sustainable use of the plants.
  • No more crop failures.

    How can they be sustained / enhanced? One should only cultivate plants that can cope with the local excess or scarcity of water.
Strengths: compiler’s or other key resource person’s view
  • Riverbank stabilisation due to the plantation of trees.

    How can they be sustained / enhanced? A good idea would be to establish a second row of trees along the river and thus enlarging the number of trees and their positive effects on riverbank stabilisation and filtering of the runoff.
Weaknesses/ disadvantages/ risks: land user's viewhow to overcome
Weaknesses/ disadvantages/ risks: compiler’s or other key resource person’s viewhow to overcome
  • After the harvest of the Napier, the land is bare and vulnerable to erosion. Instead of cutting the whole plot at once, only a quarter of the Napier grass should be cut at once. So that the land is not completely vulnerable to rain.

References

Compiler
  • Manuel Fischer
Editors
Reviewer
  • David Streiff
  • Alexandra Gavilano
Date of documentation: Jan. 28, 2013
Last update: Sept. 4, 2019
Resource persons
Full description in the WOCAT database
Linked SLM data
Documentation was faciliated by
Institution Project
This work is licensed under Creative Commons Attribution-NonCommercial-ShareaAlike 4.0 International