Investigation into problems emanating from road drainage with suggested methodology for prevention in Muranga and Baringo districts,Kenya
The report describes an investigation into the problems of soil erosion which are associated with road design, construction and drainage, Although there are many advantages to be gained from a high density road network. there are frequently adverse effects due, first, to increased runoff, secondly. the inter ception of runoff from higher ground by road drains which disrupt the natural drainage pattern and thirdly, the discharge of concentrated runoff .through pipe cross culverts. For the purpose of the investigat~on. a detailed study was carried out at two sites where serious problems had arisen. The first site was in Kandara Division of Muranga District, which is characterised by a high rainfall and steep slopes which are densely settled. Here. the erosion problem was associated with a class E road. The second site was in Eldama- Ravine Division bf Baringo District which is character ised by a less humid climate and sparser pODulation. The erosion problem was associated with a class C road. The objectives of the study were to document the erosion problem which had occurred, to establish the causes and to make recommendations for control and future prevention methods. The work undertaken included a ground survey with a telescopic level to determine the volume of soil eroded, measurement of catchment area and estima- tion of runoff. Observations on the design and (vi) construction of the present water disposal systems were made and oral interviews with government officers and farmers W0~8 carried out. The main finding is that most erosion problems arise either from failure to design and construct road drains on engineering principles or from failure to provide proper outlets to carry water from c~lverts to the main water courses. The damage being caused to farm land and the risk to valuable property caused by s.i1 erosion is enormous. High level cooperation between the relevant agencies is required for the present control and future prevention of gully erosion associated with roads.