The nature and management implications of landsliding on irrigated terraces in the Middle Hills of Nepal

SUMMARY

In the wetter areas of the Himalaya, irrigated terraces for the growing of rice (paddy) are the mainstay of the agricultural economy. Increasing population pressure is encouraging farmers to change from a single irrigated crop to double irrigation of terraces and from rainfed (bari) terraces to irrigated terraces. This change places a premium on the efficient use of the, often dwindling, water supply. As this study in the Middle Hills of Nepal has shown, irrigated terrace risers often experience extensive slope failures. Although such failures are relatively insignificant in land degradation terms, they are labour intensive with respect to remedial measures and create management problems. The results also suggest that it is the recent conversion of bari terraces to irrigated terraces that are experiencing most problems. There is also the implication that the landscape has almost reached the point where further expansion of irrigated terraces is unsustainable. If food production is to be increased, other cropping systems will need to be considered, with more attention being paid to the sustainable use of rainfed terraces.

Key words:

• slope failure
• irrigated rice terraces
• water management
• sustainability
• Himalaya
• Nepal