Sediment morphology and distribution in a restored riparian forest

Abstract

Sediment distribution patterns of riparian zones reflect the deposition dynamics and the type of deposition event. The purpose of this study is to characterize the morphology and distribution of sediments deposited in a restored riparian forest that were transported from adjacent areas cropped with sugar-cane. In order to study the deposition processes in a riparian forest located in the county of Iracemápolis state of São Paulo, Brazil, soil samples were collected on a transect for micromorphological as well as particle size distribution analyses, using Folk & Ward statistical parameters. Soil samples were dispersed with NaOH + sodium hexametaphosphate and water. The dispersion in water was made to simulate field transport conditions. Particle size distributions together with field and laboratory morphological analyses showed an irregular and non-uniform sediment deposition. This deposition process suggests the occurrence of high intensity erosive events that produce high amount of sediments and runoff characterized by a turbulent flow. The land use change in the riparian area marks the change in the preferential deposition location, which when sugar-cane dominated, corresponded to the alluvial plain and, after the restoration and development of the riparian forest, was dislocated 27 m upslope within the first few meters from the border of the forest.