Publications

ASIST Bulletin no. 8, January 1999

Investment in soil conservation along roads: Was money well spent?

Experience from the minor roads pilot soil conservation project in Kenya

By Arne Eriksson, Agrisystems, Nairobi, Kenya (acted as a project adviser)

Construction of artificial waterway to convey
water safely to a disposal point

Fear of high costs for soil conservation along roads has been a major obstacle delaying inclusion of these environmental aspects in rural road programmes.

Experience from the Kenyan Minor Roads Soil Conservation Pilot Project, which was implemented 1990-1992 by the Ministry of Public Works (MoPW) in collaboration with the Ministry of Agriculture (MoA), showed that low cost technology could be effective. The limited data available indicate that investment in soil conservation would possibly be justified by future reduced costs for road maintenance.

Conflict between road builders and farmers result in inadequate road drainage

Soil erosion caused by road drainage has been recognised as a serious problem in parts of Kenya, particularly in intensively cultivated areas in hilly terrain, and in semi-arid areas with poor vegetative ground cover. Studies showed that in some areas up to 90% of culvert out-falls cause gully erosion.

This situation has caused conflicts between the Roads Department and farmers making it almost impossible to upgrade and maintain a road to set standards, unless farmers are satisfied that measures are taken to limit soil erosion damage.

Drainage systems discharging water onto farmland, that are installed without farmers' acceptance, are often deliberately blocked by them.

Apart from looking at the road and the road reserve, the Pilot Project looked into off-road soil conservation in the catchment above the road (upper catchment) and below the road (lower catchment), and into the construction and stabilising of drainage out-falls for safe discharge of water.

Benefits from off-road soil conservation

Soil conservation is promoted as part of the Ministry of Agriculture land management programmes, with extension packages offering sufficient yield increase to be implemented without government subsidies.

Farmers adopting soil conservation measures realise that they can now control the water and make productive use of it. This change in farmers' attitudes towards viewing water as a friend instead of their enemy is a most important achievement.

Within the Pilot Project, the MoA gave priority to critical catchments above and below the road. The Roads Department consulted land owners during the planning of road drainage. As a result of shown commitment towards limiting eventual damages from water discharge, no single farmer refused to have water channelled over his or her land. Five years later, no culverts and drains along the pilot project roads have been blocked by farmers and there is generally very little erosion damage.

Expected level of benefits

i) Reduced cost for periodic maintenance

Although we have no country wide studies indicating actual levels of reduced costs for periodic maintenance, there are indications that this benefit alone could financially justify the relatively marginal additional cost for off-road soil conservation. Studies are urgently needed to find the level of expected savings.

Over an eight-year period, we find that the total cost of road maintenance, (including the initial investment in soil conservation), would be 69% of the cost for the alternative without soil conservation.

ii) Repairs as compared to prevention

The following example illustrates the cost difference between prevention and repairs.

Road E 560 runs between Nyeri and Murang'a Districts. Four kilometres were constructed with soil conservation measures, and four without.

In 1997, five years after construction, there was still no soil erosion damage on the section with soil conservation despite no maintenance work being carried out.

Three years after construction, most of the culverts (twelve) along the section without soil conservation have developed gullies, gradually eating away the road (culvert rings are already falling one by one into the gullies). The cost of repairs is estimated to be 2.7 times higher than the cost of prevention.

Comparing the present net value of expenditure with and without soil conservation shows that waiting for repairs to be carried out three years after the road is constructed would cost two times as much as prevention would have cost initially.