Effect of design factors for groynes on diversification of topography and restoration of ecosystems in straight and meandering streams

Abstract

In this study, we investigated effectiveness induced by the installation of groynes in river for protection of stream and restoration of ecosystem in Korea. The effect of different designs in groyne including shapes (single-bar type and double –bar type), angles (45° and 135° to the stream flow), and intervals (1 m and 2 m between groynes) on topographic changes were examined in test bed. The topographic changes in different cases were analyzed and compared both qualitatively and semi-quantitatively. More various topographical changes were found in the case with the installation angle of 45°, double-bar type groyne, and 2 m-interval by significant erosion or switching pattern of erosion and deposition along the stream. Comparative analysis results implied that this switching pattern would be the response from properly designed groynes. Based on results from test bed, 13 groynes were installed in the field and topographical changes with biodiversity were observed after installation. As evidences on the effectiveness of groynes, the formation of shallow puddles and increases in number of fishes and invertebrates were observed in the field.