Morphologic evolution of macrotidal estuarine channels in Gomso Bay, west coast of Korea: Implications for the architectural development of inclined heterolithic stratification

作者：Choi Kyungsik^*; Hong Chang Min; Kim Mi Hee; Oh Chung Rok; Jung Jae Hoon

来源：Marine Geology, 2013, 346: 343-354.

DOI：10.1016/j.margeo.2013.10.005

• macrotidal channel
• inclined heterolithic stratification
• channel migration
• meander-bend cutoff
• rainy season

Temporal variation of intertidal-channel morphology was monitored using a RIK GPS over three years in the macrotidal embayment of Gomso Bay, west coast of Korea. Intertidal channels have highly sinuous meander planforms with well-defined point bars and cutbanks. The channels are classified into three size categories, i.e., main channels, large tributary channels and small tributary channels. Main channels range in width between 200 and 400 m and are up to 4 m deep at bankful stage. Large tributary channels are 100-150 m wide and up to 3 m deep at bankful stage. The width and depth of small tributary channels are smaller than 10 m and 15 m, respectively. Channels migrate laterally to produce variably dipping inclined heterolithic stratification (IHS) that constitute convex-up point bar deposits. The migration rate of point bars range between 0.5 m/month and 3 m/ month, being greatest during the summertime rainy season. Whereas the channel thalweg migrated actively, bank erosion is not prominent except for the rainy season when the cutbank retreated as fast as 3 m/month. The channel-migration rate also varies with elevation and location, being greatest in the upper intertidal zone and at the large tributary channel, respectively. An IHS rarely reaches a thalweg level presumably due to the presence of strong ebb currents. The initiation of incipient ebb-chute channels leads to meander-bend cutoff and simultaneous channel abandonment which occur over several to tens of months. Thalweg level gradually falls in the chute channel while it is on the rise in the abandoned large tributary channel, producing an inclined layer of channel lag. The abandoned large tributary channel continues to migrate until it is completely filled up with sediments. Measured sedimentation rate in the abandoned large tributary channel reaches up to 20 cm/month. IHS contains erosion surfaces generated by ebb-chute channels and rill channels. Such erosion features as well as morphologic change are most prominent during the summertime rainy season, when ebb currents are reinforced by increased runoff discharge. Despite the macrotidal regime and small fluvial upstream reach, long-term evolution of tidal channels in Gomso Bay seems to be governed largely by the intensity and frequency of seasonal flooding.

• 出版日期2013-12-1