Progress of a Sedimentation using a Nakdong Estuary information Service System (NEiSS) data in the Nakdong River Estuary (NRE), Busan M etropolitan City, South Korea

Abstract

The Nakdong River in South Korea is a length of nearly 510 km with a drainage basin of around 23,384 km and is subject to natural erosion, sedimentation and various potential sources of human development, due to a number of anthropogenic factors, including relative water diversion, reservoir construction, and large river-estuary engineering. The Nakdong River Estuary (NRE) barrage (floodgate, weir and dyke) in Busan city, South Korea was completed in November 1987 to regulate flow from the Nakdong River. This study is progress of a sedimentation using a Nakdong Estuary information Service System (NEiSS) to understand the land–sea interaction and provide scientific data on the characteristics of the brackish water zone around the barrier islands in the NRE from 2015 to 2021. In the stratification index analysis, main stream NRE barrage showed a distinctive salt wedge estuary type showing stratification during both the ebb and flood. The NRE barrage has been characterized as barrier-lagoon system with 14 a priori groups subenvironments. The scientific data include periodic observations of sediment distributions (N=90). The surface sediments generally showed sand sediment was dominated in the seaward side of barrier islands and muddy sand sediment was dominated on the lagoon. In 27 August 2015, Depth-integrated net suspended sediment loads (Q) for one tidal cycle showed seaward movement of 1,698.4 kg·m-1 (net suspended sediment flux (F) of surface, middle and bottom is –2.1·10-3 , –2.0·10-3 and +3.3·10-3 kg·m-2·s-1 , respectively). The NEiSS will enable effective estuary management and contribute to predict the NRE environmental change caused by partial opening due to the drainage extension of NRE barrage, 2019. Moreover, it is possible to use comparative data of the characteristics of environmental changes in this estuarine watershed to prepare the NRE for the always opening of barrage in 18 February 2022.