At present, approximately 30% of coasts are experiencing net erosion in the Changjiang Delta and the North Jiangsu coastal plain. Future sea level rise will accelerate the process of coastal erosion. According to the ratio of the calculated value of coast retreat by Bruun rule to the estimated value by using measured data, the proportion affected by sea level rise in total coastal erosion has been estimated in this paper. When sea level rises 20cm, the proportion determined by sea level rise will increase from 1.0% at present to 2. 2% in the future in the coasts of the Abandoned Yellow River Delta and from 8. 5%-9. 6% to 13. 5%-15. 2% in the north and south coasts of the Changjiang Delta. This result is lower than that from the similar research in the world, and this phenomenon is related with the special development process of the coasts in this area. In the coasts of the Abandoned Yellow River Delta, coastal erosion is due to the sediments deficiency since the Yellow River returned to its north route in 1 855, but in the coasts of the Changjiang Delta, there are rich in sediments, coastal erosion is mainly due to strong hydrodynamic action. Judged by the range of near-future sea level rise, sea level rise will not become a controlled factor of coastal erosion in this area.
The mechanism of accelerating coastal erosion by sea level rise is that sea level rise will increase the intensity of tidal current, wave and storm surge and decrease the ability to reduce the force of waves on the tidal flat and coastal wetland due to the loss of their areas. Therefore, the length of erosion coasts will increase, the sedimentation rate of accretion coasts will decrease or even turn accretion into erosion, the width of tidal flat will reduce and coastal slope will increase. So the project of coastal protection of this area must be reinforced.
Acta Geographica Sinica