Evaluation of factors influencing water erosion in West Africa using rainfall simulation

I n o r d e r t o provide an improved understanding of t h e f a c t o r s i n f luenc ing water e ros ion i n western Africa, f i e l d s t u d i e s were c a r r i e d ou t i n t h r e e c o u n t r i e s ( Ivory Coast , Upper Volta and Niger) . Two types of r a i n f a l l s imu la to r were used. given t o t h e i n t e n s i t y d u r a t i o n cu rves , t h e k i n e t i c energy of t h e s to rms , and t o t h e range of antecedent s o i l moisture cond i t ions . Treatments were s e l e c t e d i n accordance wi th t h e farming systems p r e v a i l i n g i n t h e s tudy areas. un&er n a t u r a l r a i n f a l l . They suggested t h a t s u r f a c e g rave l and cobbles are very e f f e c t i v e i n reducing e ros ion . I n t h e humid t r o p i c s , t h e e ros ive e f f e c t s of storm ra in f a l l are o f f s e t by t h e n a t u r a l p r o t e c t i o n provided by t h e vege ta t ive cover . The e f f e c t i v e n e s s of t r a d i t i o n a l conse rva t ive p r a c t i c e s depends upon t h e s o i l w a t e r i n f i l t r a t i o n . c o l l a p s e and as a r e s u l t e ros ion is s t r o n g l y enhanced. Likewise, t h e e f f i c i e n c y of r e s i d u e mulch depends upon t h e t e x t u r e of t h e t o p s o i l . i n a n t use of t h e Universal S o i l Loss Equation which inc ludes f a c t o r s which are assumed t o be independent can be h igh ly hazardous. E s t i m a t i o n des f a c t e u r s de 1'6rosion h y d r i q u e en n f r i q u e d e l ' o u e s t A l ' a i d e de l a s i m u l a t i o n d e p l u i e s RESUME D e s t r avaux de t e r r a i n on t été menés dans t r o i s pays-(Côte d ' I v o i r e , Haute Volta e t Niger) a f i n de f o u r n i r davantage de données concernant les d i f f é r e n t s f a c t e u r s q u i i n t e rv i ennen t s u r l ' é r o s i o n hydrique e n Afrique de l ' o u e s t . Deux types de s imula t eu r s de p l u i e s on t été u t i l i s é s . Une grande a t t e n t i o n a été portée aux courbes in t ens i t é -du rée , 2 l ' é n e r g i e c i n é t i q u e des p l u i e s , e t 3 l a gamme d 'humidi tés avant l e s averses. Les t r a i t e m e n t s on t été c h o i s i s en f o n c t i o n des systèmes cu l tu raux q u i prédominent dans les d i v e r s e s régions d 'é tudes. L e s r é s u l t a t s s o n t conformes 2 ceux obtenus sous p l u i e s n a t u r e l l e s . Ils expriment l ' importance des éléments g r o s s i e r s s u p e r f i c i e l s quant 'a l a conservat ion des s o l s . En m i l i e u t r o p i c a l humide une p r o t e c t i o n n a t u r e l l e est a s su rée p a r l e couvert v é g é t a l q u i compense a i n s i les effets n é f a s t e s des p l u i e s très v i o l e n t e s . L ' i n f luence des techniques t r a d i t i o n n e l l e s de Lu t t e an t i é ros ive est . l i ée aux q u a n t i t é s d 'eau i n f i l t r é e : 2 p a r t i r d 'un c e r t a i n P a r t i c u l a r a t t e n t i o n was Resu l t s w e r e c o n s i s t e n t w i th those obtained Above c e r t a i n th re sho ld va lues , r i d g e s Consequently, t h e indiscr im.