impacts of anthropogenic alterations on the Yeongsan estuary, South Korea

초록

Extensive anthropogenic alteration to the macro-tidal Yeongsan Estuary has been the result of vast coastal construction of seawalls and emplacement of an estuarine dam (1981). The impacts have been assessed from 30 gravity cores utilizing 210Pb radioisotope geochronology, laser diffraction particle analyses, δ13C and δ15N isotope ratio mass spectrometry, and X-radiography. Average sediment accumulation rates range significantly from 0.9 ± 0.6 cm yr-1 to 10.0 ± 2.9 cm yr-1, side scan sonar collected adjacent to the dam reveals distinctive scouring and a transition zone to fine-grained sediments, and changes in the organic matter sources are apparent in pre/post-dam sediments. Additionally, cores collected associated with periods of limited and high discharge were analyzed for 7Be, indicating sedimentation occurs episodically corresponding to dam releases. Our observations record a shift in depositional environments as a natural response to an extensive array of anthropogenic alterations. Ultimately, a reduction in the tidal prism, land reclamation, and estuarine dam construction have increased the sediment trapping efficiency and severely altered the fate and transport of sediments.