Performance of gully erosion control measures in southeastern Nigeria

Abstract

The performance of gully erosion control measures in some parts of southeastern Nigeria is presented. The measures include tree planting, hydraulic regulation works that integrate a drainage network with storage ponds to cut off flood crests and lower hydraulic loads of interceptor canals, and stabilization works such as check dams on the main channels of gullies and wicker- work fences and hedges at the inner gully slopes. There is evidence that tree planting and surface regulation of surface waters is effective in controlling only shallow «15 m deep) gullies that have not cut through a satu- rated zone. These measures tend to fail when used for deep gullies that are greatly affected by groundwater especially when such gully floors are located in non cohesive and very permeable sands. Performance de mesures de controle du ravinement dans Ie sud-est du Nigeria RESUME La performance de controle du ravinement a ete evaluee pour les mesures suivantes: reboisement, ouvrages de regularisation hydraulique comprenant reseaux de drainage et etangs d'emmagasinement visant a diminuer les pics des crues et les charges hydrauliques des canaux d'interception, et ouvrages de stabilisation tels que digues dans les ravins principaux et clotures et haies de vannerie sur les pentes de ces ravins. Les resultats suggerent que Ie reboisement et les ouvrages hydrauliques sont efficaces face ades ravins peu profonds «15 m) qui n'ont pas atteints de zones saturees. Ces mesures echouent sur des ravins profonds qui interceptent la nappe phreatique, particulierement si Ie fond de ces ravins est dans des sables permeables non cohesifs.