Many rivers in semi-arid areas of Kenya are seasonal in nature, flowing only during the rainy season. Such rivers usually overflow their banks and change course due to high volume of water that flows at high speed. Kitui County, which has many such rivers is situated in a semi-arid region of Kenya and has temperatures ranging between 260C - 340C and annual rainfall of between 300 mm – 1,050 mm. In Kitui County, seasonal flooding causes rivers to change course by cutting through and extending the riverbed leading to soil erosion, formation of gullies and reduction of productive agricultural land. Although construction of gabions has been used to control the seasonal river floods, these structures can be destroyed by river overflow. An option that can offer a long lasting solution to river bank stabilization is planting of Bamboo along the river bank. Bamboo is well known for river bank stabilization due to its rhizomes, fibrous and deep roots.
The objective of planting bamboo is to stabilize river banks and restore degraded farming land.
To establish bamboo seedlings along a river bank or in a gully, dig holes measuring 45 cm wide by 45 cm long by 45 cm deep, spaced at 3 m apart before the onset of the rains. Plant the seedlings during the September - December rains, commonly referred to as the short rains. Plant one bamboo seedling in the middle of each hole. The seedlings should be weeded twice before the rainy season for the first two years. Fencing should be done to protect bamboo seedlings from browsing by animals.
|Degraded Mwewe River bank in Kitui County
||Stabilized river bank
|Preparation of holes for bamboo planting in a gully
||Successfully reclaimed land
Through planting bamboo along river bank and gullies on-fam, farmers are able to improve their livelihood by rehabilitating and reclaiming agricultural land. Other benefits include;
- Socio-economic: Increased farm income from crops and fodder grown on reclaimed land.
- Socio-cultural: Improved food security, and health
- Environmental: Reduced soil erosion; Improved biodiversity and resilience to floods and storms; and Increased vegetation cover and animal habitat.
Innovations and Success Factors
The success of river bank stabilization using bamboo can be enhanced by the following innovations:
- Doubling planting hole size to 90 cm wide by 90 cm long by 90 cm deep. This increases the water catchment, hence improving survival of the bamboo plants.
- Reducing the spacing between the holes to increase compactness of the soil by the bamboo plants.
- Introducing a mixture of sand, manure and soil at a ratio of 1:1:2 to fill the planting holes to improve establishment of the bamboo plant.
- Planting fodder grasses such as napier between the bamboo plants to enhance the stabilization of the soil.
- Arranging the rows of holes in a curvilinear design to reduce soil erosion and the speed of the water runoff.
- Planting indigenous grasses that check the rapid flow of water, hence reducing soil erosion.
- Diversifying on-farm investments to generate income that subsidizes the cost of labour and bamboo seedlings.
- Using dry river bed harvested water to irrigate reclaimed land to counter the prolonged droughts
The main constraint is unavailability and high cost of bamboo seedlings.
A species like bamboo with deep fibrous roots is good for stabilizing river banks. However river banks stabilization can be enhanced through introduction and inter planting of bamboo with other valuable grass species.
Bamboo has potential of stabilizing degraded river banks and reclaiming eroded gullies. However, there is need for training farmers on bamboo propagation, establishment, management and utilization.
We acknowledge Mr. Gideon Masila and his farm manager Mr. Joseph Mailu for sharing information which enabled the compilation of this good practice.
Joyce Okumu, Dr. Ebby Chagala- Odera, Samson Mogire, Florence Mwanziu, Damaris Munyao, Dr Michael Mukolwe, Victor Gitau Kamau and Yuki Honjo