Sediment from the upstream channel has been deposited near the Nakdong River Estuary Barrage (NREB) due to the mild slope and decreased velocity. The annual mechanical dredging to ensure the flood capacity has been performed to remove the deposited sediment. However, the dredging method is not considered as an effective countermeasure due to high cost and long time to operate. Therefore, many methods for sedimentation reduction have been proposed for NREB. Especially, the channel contraction method to mitigate sedimentation problem by changing the channel geometry from 2 km to 3 km upstream of NREB has been recently suggested as an effective countermeasure. However, there is the possibility that the channel contraction method induces flood level increase compared to original condition. Therefore, it is necessary to investigate quantitatively the flood level changes in the upstream and downstream section due to the channel contraction method for NREB. In this study, water level changes by 10% channel contraction of whole width has been evaluated using the HEC-RAS model and simulated with and without channel contraction for various flood discharge. As a result, water level in the section where the channel was contracted was decreased by 0.02 m and flood level at the upstream of channel contracted was increased up to 0.015 m for the 500-year flood.

Abstract
 1. 서 론
 2. 재료 및 방법
  2.1. 대상하천의 개요
  2.2 모의 조건 및 하폭축소 지형
 3. 결과 및 고찰
  3.1. 홍수위 변화 분석
  3.2. 하상변동 모의 결과 및 분석
 4. 결 론
 참 고 문 헌

• 장은경(명지대학교 토목환경공학과) | Eun-Kyung Jang (Dept. of Civil and Environmental Engineering, Myongji University)
• 지운(한국건설기술연구원 수자원환경연구본부 하천해안연구실) | Un Ji (River and Coastal Research Division, Department of Water Resources and Environment Research, Korea Institute of Construction Technology) Corresponding author