The Effects of Reclamation Activity and Yellow River Runoff on Coastline and Area of the Laizhou Bay, China

Study on morphological changes of a bay can help to identify the effects of anthropogenic activities on coastal environment and guide the exploration of marine resources. In this paper, morphological data including coastline and water areas in five discrete years between 1968 and 2015 were selected and extracted from the remote sensing images and historical marine charts to study the morphological changes in Laizhou Bay (LZB), one of the bays in the southwest of the Bohai Sea. A systematic analysis on spatial variations of the coastline and the surface areas of different types of waters in LZB was conducted. The results showed that the surface area of LZB was decreased by 1253.2km(2) in the last half century, which is 17.4% of the total in the 1970s. The areas of the natural wetland and the intertidal zone were decreased by 17.2% and 56.1%, respectively, and the average water depth varied from 9.05m to 8.16 m at low tide level from 1968 to 2015. The coastline and shape variations of the bay turned to be complex after the 1980s, and the shape index of LZB showed an increasing trend in more recent years. The centroid of the bay generally migrated to the northeast direction, i.e., the direction of the center of the Bohai Sea, and the shrinking direction of the bay was consistent with the migration direction of the coastline. The reclamation area during 1968-2015 in LZB was 1201.7 km(2), and 94.1% was in the inter-tidal zone. The overall morphological change of the bay during the last half century was mainly controlled by the coastal reclamation activities, and the Yellow River runoff including the river course change and sediment load variation was also an important controlling factor.

Automated summary

This study on morphological changes in Laizhou Bay over the past half century revealed that the main factor influencing the changes was coastal reclamation activities, with the Yellow River runoff also playing an important role in controlling these changes.