Land user brings the wood logs to the rice field to make barriers (Vadsana Boualaivan)

Logs to reduce surface run-off during the rainy season (Lao People's Democratic Republic)

Description

Logs to reduce surface run-off during the rainy season.

In the upland areas with 3-5 % at foot slopes and 16-30% hill slopes of Lao PDR rotational shifting cultivation has been the primary means of the local people’s livelihood for many generations. Given the topography of the area with its hill slopes it restricts the opportunities for agricultural development. After the land on foot slopes has been cleared and the remaining vegetation burned off in preparation for agricultural activities there are significant impacts on land use particularly during the rainy season which occurs between May-November. There are heavy downpours especially in the months of September and October that create significant sediment transport along the mountain valleys and it also results in flushing organic matter on the surface being flushed along the road sides and ending up in waterways. Furthermore decayed vegetation is washed over the crops. The negative impacts experienced from the loss of fertile topsoil motivated many of the land users to develop some kind of technology in 2015 that could control this run-off from the mountains.
This technology was also meant to help maintain nutrient levels on topsoil as without a technology the nutrients are being flushed down the hillside. It can be assembled using a collection of local logs approximately 4-5 meters in length and around 15-20 cm in diameter (obtained through the clearance of upland rice fields). The logs should be arranged horizontally at the position of a designated drainage site where the run-off flows from a particular agricultural area. They should be stacked on top of one another until reaching a height of about 1 meter. A buttress should also be erected using mature bamboo poles as supporting posts with a length of 1.5 meters and diameter of about 10 cm so as to prevent the logs from sliding down the hillside. The bamboo poles should be driven about 50 cm into the ground and then tightened with ropes. This technology should only be constructed after the planting of upland rice fields has been completed in mountainous areas which have slopes between 20-25%. In general, the local residents have set up this mechanism at 2-3 selected sites within an agricultural plot. The benefits of this technology include mitigating the impacts of soil run-off whilst facilitating the distribution of soil nutrients around the agricultural plot of land. The water and top soil run-off is slowed down when it reaches the log wall and is then directed to flow out on either side of the technology. Previously the average rice yield used to be 1.5 tons/ha, but then the upland rice yields increased to 2 tons/ha after the application of this technology. This is due to the reduction of soil surface losses and an increase in the soil’s organic matter that accumulates through the processes of sedimentation and biomass transport. The quality of the surrounding soil improves through the decay of biomass and the breakdown of the soil by organisms such as earthworms and millipedes.
This technology can be installed on hill slopes . The technology is approximately 1 meter in height (above ground) and 4 -5 meters in length. The supporting posts need to be driven 50 cm into the ground. This technology can be used at the location of seasonal drainage points or water channels on hill slopes between 20-25% (with usually 2 or 3 sites per agricultural plot).

Strengths: Reduces sediment run-off, increases organic matter on the soil’s surface (builds a thicker layer of soil), financially economical, and distributes nutrients on agricultural plots.

Weaknesses disadvantages/ risks of the technology/ how to overcome them: Most of these technologies are not permanent and quite exposed and therefore require annual repair and maintenance. If the run-off facility is to be upgraded, it would need the use of a better quality of rope and concrete posts. However, most people still use the readily available local materials which affects the quality of the water run-off technology as well as its effectiveness. Furthermore this technology may need to be installed at several sites along the same channel on the foot slopes.

Location

Location: Phouvong District, North Vongvillay village, Attapue Province, Lao People's Democratic Republic

No. of Technology sites analysed: single site

Geo-reference of selected sites
  • 106.83247, 14.66049

Spread of the Technology: applied at specific points/ concentrated on a small area

In a permanently protected area?:

Date of implementation: 2015; less than 10 years ago (recently)

Type of introduction
Farmer using wooden logs for the construction of a cross-slope barrier fixed by bamboo plants. (Vadsana Boualaivan)
Wooden logs residues as barrier against water flow, spread sediment and change water way to production area (Vadsana Boualaivan)

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

  • Cropland
    • Annual cropping: cereals - maize, cereals - rice (upland), root/tuber crops - cassava
    • Perennial (non-woody) cropping: banana/plantain/abaca, sugar cane
    Number of growing seasons per year: 1

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, Wo: offsite degradation effects
SLM group
  • cross-slope measure
SLM measures
  • structural measures - S6: Walls, barriers, palisades, fences, S11: Others

Technical drawing

Technical specifications
The technique is applied on foot slope area
Wooden log barriers are created with hight of 1 meter from the surface.
The length of the logs is about 4-5 meters .
Depth of the bamboo post into the soil is 50 centimeters to hold the logs,
This technique is implement on the top of the rice field at the slope 20-25%, where the water form natural surface canals.
Author: Vadsana Boualaivan

Establishment and maintenance: activities, inputs and costs

Calculation of inputs and costs
  • Costs are calculated: per Technology unit (unit: 2 wooden log barriers volume, length: Width: 4-5 meters / High 1 meter (1 barrier))
  • Currency used for cost calculation: kip
  • Exchange rate (to USD): 1 USD = 8000.0 kip
  • Average wage cost of hired labour per day: 50000
Most important factors affecting the costs
The equipment is the most important factor affecting the costs.
Establishment activities
  1. Collect the wood logs and bamboo postsv (Timing/ frequency: After harvesting)
  2. Bury the bamboo post (Timing/ frequency: None)
  3. Arrange the wood (Timing/ frequency: None)
Establishment inputs and costs (per 2 wooden log barriers)
Specify input Unit Quantity Costs per Unit (kip) Total costs per input (kip) % of costs borne by land users
Labour
labor ( for two barriers ) person-day 2.0 50000.0 100000.0 100.0
Equipment
hoe piece 1.0 50000.0 50000.0 100.0
shovel piece 1.0 25000.0 25000.0 100.0
hummer piece 1.0 20000.0 20000.0 100.0
Plant material
timber logs (for two barriers) piece 10.0 100.0
bamboo (for two barriers ) stick 10.0 100.0
Total costs for establishment of the Technology 195'000.0
Total costs for establishment of the Technology in USD 24.38
Maintenance activities
  1. Repair of the barrier (Timing/ frequency: 2 times a year)
Maintenance inputs and costs (per 2 wooden log barriers)
Specify input Unit Quantity Costs per Unit (kip) Total costs per input (kip) % of costs borne by land users
Labour
labor (for two barriers ) person 2.0 50000.0 100000.0 100.0
Equipment
knife piece 2.0 25000.0 50000.0 100.0
shovel piece 1.0 20000.0 20000.0 100.0
Construction material
timber ( for two barriers ) piece 10.0 100.0
bamboo ( for two barriers ) stick 10.0 100.0
Total costs for maintenance of the Technology 170'000.0
Total costs for maintenance of the Technology in USD 21.25

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: 2500.0
From May to September there is more rain, highest between July and September and it decreases to lowest from November to April
Name of the meteorological station: Phouvong district natural resource office
The average annual temperature is 26.2 °C
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
good
education

poor
good
technical assistance

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

poor
good
markets

poor
good
energy

poor
good
roads and transport

poor
good
drinking water and sanitation

poor
good
financial services

poor
good

Impacts

Socio-economic impacts
Crop production
decreased
increased

Quantity before SLM: 1.5 ton/ha
Quantity after SLM: 2 tons/ha
Increase in organic matter from surface accumulation

production area (new land under cultivation/ use)
decreased
increased


Before farmer lossed a lot of surface due to the water channels in the cultivation area; after wood log barriers has been constructed runoff stopped, and surface area increased by soil accumulation

farm income
decreased
increased


Previously water flow on the production area caused damages to crops and in consequence reduced crop yield

workload
increased
decreased


Installing wood log barriers to extend the cultivation area requires more labour

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


Food security has been improved because the farmer get more yield and can sale the surplus even in the local market

Ecological impacts
surface runoff
increased
decreased


The water and top soil run-off is slowed down when reaching the log barrier and the water is directed on either side. Thus, heavy surface runoff is stopped efficiently.

soil loss
increased
decreased


Before a lot of top soil by water leaching on the soil surface was lost. After the installation of the wooden log barrier water way changed and spread sediments to the area and reduced accumulation in the road canal

biomass/ above ground C
decreased
increased


Wooden log barriers can spread biomass and plant fragment and sediment to production area (increase topsoil)

landslides/ debris flows
increased
decreased


Before heavy rains caused soil erosion (rill or sheet erosion between row) in rainy season

Off-site impacts
damage on neighbours' fields
increased
reduced


Before water way flow through owners land. After the installation of the technology the water way was changed to neighborhoodt without causing damages there.

Sediment run-off into the road canal
decrease
increase


Before the sediments from the rill erosion went directly into the road canal. After wood logs installation sedement remained mostly on the field

Cost-benefit analysis

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

Long-term returns
very negative
very positive

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

Long-term returns
very negative
very positive

Climate change

Gradual climate change
annual temperature increase

not well at all
very well
seasonal temperature increase

not well at all
very well
Season: wet/ rainy season
annual rainfall increase

not well at all
very well
seasonal rainfall increase

not well at all
very well
Season: wet/ rainy season
Climate-related extremes (disasters)
local rainstorm

not well at all
very well
extreme winter conditions

not well at all
very well
drought

not well at all
very well
forest fire

not well at all
very well
landslide

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

not well at all
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
  • Reduce sediment run-off
  • Increased organic matters on soil surface (create thicker soil layer)
  • Low cost for implementation
Strengths: compiler’s or other key resource person’s view
  • Better distribution of nutrients on agricultural lands.
Weaknesses/ disadvantages/ risks: land user's viewhow to overcome
  • Most of these facilities are not permanent and vulnerable which require repair every year It may require better rope quality and concrete posts.
  • Some sediment accumulation are still caused by remaining run-off sites must create many point of barrier
Weaknesses/ disadvantages/ risks: compiler’s or other key resource person’s viewhow to overcome
  • People still use available local materials which affects the quality of the water run-off facility as well as its effectiveness. It may require installation of this kind of facility in many sites along the same channel depending on slope of the land.

References

Compiler
  • kang phanvongsa
Editors
  • Vardsana Buavanxay
  • Bounthanom Bouahom
Reviewer
  • Nicole Harari
  • Stephanie Jaquet
  • Alexandra Gavilano
Date of documentation: May 18, 2017
Last update: May 10, 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