Sediment transport in small streams is related to riparian buffer width : a comparison between wide and narrow riparian buffers

University essay from SLU/Dept. of Forest Ecology and Management

Abstract: This study aims to provide information about how different widths of riparian buffers affect the quantity and quality of sediments transported in a small stream after a clear – cut harvest. Small streams have critical influences on downstream rivers and excessive transported sediments can have large negative effects on the aquatic system. A small stream located 45 km north-west from Umeå, Sweden was studied. Traps were used to catch sediments transported along the stream bottom at the end of 100 m long sections of stream that either had a narrow (5m) or wide (15m) riparian buffer or was located within intact forest. The sediment collected was separated into coarse sediment, fine sediment and very fine sediment. A narrow riparian buffer was found to cause significantly (p < 0.05) heavier amounts of coarse transported sediments than a wide riparian buffer after a clear – cut harvest. A narrow riparian buffer caused heavier weights of transported sediments from the pre-harvest and the un-harvested control than the wide riparian buffer. After a clear – cut harvest, the amount of inorganic transported sediments weighed significantly (p < 0.05) more than the amount of organic transported sediments. Additionally, it was found that a wide buffer could produce larger amounts of coarse organic transported sediments than a narrow buffer – at least during a wind and rain storm. With the results from this study, and with support from previous studies, it is suggested that a wide riparian buffer should be used when a clear – cut harvest is made. The wide riparian buffer will better meet the Swedish management objectives regarding sedimentation than a narrow one.

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