Effects of Heavy Rainfall on Sedimentation in the Tidal Salt Marsh of Suncheon Bay, South Korea

Abstract

Tide observations, geographic surveys, sediment composition, and sediment accretion rate monitoring were conducted to investigate the relationship between general pattern changes and control factors of the accretion rate at 10 localities of the tidal salt marsh of Suncheon Bay over 2 years (June 2007 May 2009). The substrate sediments of the tidal salt marshes that are distributed between the mean sea level and the high water of ordinary spring tide are mainly composed of silt (37.98%) and clay (60.45%) and have a high average annual accretion rate of 28.88 mm/y. The high substrate sedimentation of tidal salt marshes is caused by: (1) a high concentrated suspended sediment supply from the tidal flat; (2) considerable marsh grass vegetation; (3) undeveloped tidal salt marsh creek; and (4) marsh elevation distributed between the mean sea level and the high water of ordinary spring tide. The variation in patterns of the average monthly accretion rate can be divided into three stages: the low stage (June 2007 to February 2008) was the period of lowest accretion rate over 2 years and consistently measured between 5.35 mm and 12.40 mm, averaging out to 8.89 mm that period. The recovery stage (March 2008 to October 2008) was a period of rapid increase in accretion rate and measured from 14.93 ram to 49.47 ram with an average of 33.02 ram. The high stage (November 2008 to May 2009) was a period of high deposition in accretion rate, and measured between 46.67 ram and 53.38 mm, averaging to 49.83 mm. These three stages were formed and changed by heavy rainfall brought about by typhoons in the summer season of Korea and undeveloped tidal salt-marsh creek system. It was confirmed that heavy rainfall may significantly alter the sediment flux within the marsh system in this study.