Measurements of rain splash on bench terraces in a humid tropical steepland environment

✍ Scribed by A. I. J. M. Van Dijk; L. A. Bruijnzeel; S. E. Wiegman

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 377 KB
• Volume: 17
• Category: Article
• ISSN: 0885-6087
• DOI: 10.1002/hyp.1155

✦ Synopsis

Abstract

Soil loss continues to threaten Java's predominantly bench‐terraced volcanic uplands. Sediment transport processes on back‐sloping terraces with well‐aggregated clay‐rich oxisols in West Java were studied using two different techniques. Splash on bare, cropped, or mulched sub‐horizontal (2–3°) terrace beds was studied using splash cups of different sizes, whereas transport of sediment on the predominantly bare and steep (30–40/deg ) terrace risers was measured using a novel device combining a Gerlach‐type trough with a splash box to enable the separate measurement of transport by wash and splash processes. Measurements were made during two consecutive rainy seasons. The results were interpreted using a recently developed splash distribution theory and related to effective rainfall erosive energy. Splash transportability (i.e. transport per unit contour length and unit erosive energy) on the terrace risers was more than an order of magnitude greater than on bare terrace beds (0·39–0·57 versus 0·013–0·016 g m J^−1^). This was caused primarily by a greater average splash distance on the short, steep risers (>11 cm versus c. 1 cm on the beds). Splashed amounts were reduced by the gradual formation of a protective ‘pavement’ of coarser aggregates, in particular on the terrace beds. Soil aggregate size exhibited an inverse relationship with detachability (i.e. detachment per unit area and unit erosive energy) and average splash length, and therefore also with transportability, as did the degree of canopy and mulch cover. On the terrace risers, splash‐creep and gravitational processes transported an additional 6–50% of measured rain splash, whereas transport by wash played a marginal role. Copyright © 2002 John Wiley & Sons, Ltd.