Effects of a Low-Head Dam Removal on River Morphology and Riparian Vegetation: A Case Study of Gongreung River

Abstract

The long term existence of a low-head dam in the river channel significantly affects river geomorphology and river ecosystem. Because more and more low-head dam structures have deteriorated in recent years, the attention for low-head dam removal is increasing as one of alternatives for river restoration. Thus, this study intends to investigate the impacts of low-head dam removal on river geomorphology and riparian vegetation with developing a quantitative method to predict the changes of river morphology as well as invasion, growth, expansion and destruction of riparian vegetation after a low-head dam removal. To verify the numerical simulation model, the low-head dam removal case in Gongreung River was employed with investigation of low-head dam removal responses on river geomorphology and riparian vegetation. Following the low-head dam removal, the results of monitoring and numerical simulation indicated that new sand bars has formed as well as increasing the extent of existing sand bars in the upstream of the low-head dam. The sand bars have been colonized in a year after the low-head dam removal by grass type plants. After a decade to several decades, the riparian vegetation in sand bars often developed to tree type plants in several low-head dam removal cases. As other cases, Gongreung River also showed the growth of tree type plants in 5 years after the removal.