Analysis of Shoreline Changes in Ikoli River in Niger Delta Region Yenagoa,Bayelsa State Using Digital Shoreline Analysis System(DSAS)

The use of Digital Shoreline Analysis System was used to determine shoreline changes in Ikoli River,Yenagoa,Bayelsa State.Shoreline data were extracted from satellite imagery over thirty years(1991-2021).The basis of this study is to use Digital Shoreline Analysis System to determine erosion and accretion areas.The result reveals that the average erosion rate in the study area is 1.16 m/year and the accretion rate is 1.62 m/year along the Ikoli River in Ogbogoro Community in Yenagoa,Bayelsa State.The mean shoreline length is 5.24 km with a baseline length of 5.2 km and the area is classified into four zones to delineate properly area of erosion and accretion based on the five class of Linear regression rate,endpoint rate and weighted linear rate of which zone Ⅰ contain very high erosion and high erosion with an area of landmass 255449.93 m^(2) of 38%,zone Ⅱ contain moderate accretion,very high accretion and high accretion with a land area of 1666816.46 m^(2) with 24%,zone Ⅲ has very high erosion and high erosion with an area of landmass 241610.85 m^(2) of 34% and zone Ⅳ contain moderate accretion and high accretion with land area 30888.08 m^(2) with 4%.Out of the four zones,zone Ⅰ and Ⅱ were found to be eroding with 72% and zone Ⅱ and Ⅳ contain accretion with 28%.The result shows that 44% of the area have been eroded.Therefore,coastal engineers,planners,and shoreline zone management authorities can use DSAS to create more appropriate management plans and regulations for coastal zones and other coastal parts of the state with similar geographic features.

Study on Headland-Bay Sandy Coast Stability in South China Coasts

Headland-bay beach equilibrium planform has been a crucial problem abroad to long-term sandy beach evolution and stabilization, extensively applied to forecast long-term coastal erosion evolvement and the influences of coastal engineering as well as long-term coastal management and protection. However, little concern focuses on this in China. The parabolic relationship is the most widely used empirical relationship for determining the static equilibrium shape of headland-bay beaches. This paper utilizes the relation to predict and classify 31 headland-bay beaches and concludes that these bays cannot achieve the ultimate static equilibrium planform in South China. The empirical bay equation can morphologically estimate beach stabilization state, but it is just a referential predictable means and is difficult to evaluate headland-bay shoreline movements in years and decades. By using Digital Shoreline Analysis System suggested by USGS, the rates of shoreline recession and accretion of these different headland-bay beaches are quantitatively calculated from 1990 to 2000. The conclusions of this paper include that （a） most of these 31 bays maintain relatively stable and the rates of erosion and accretion are relatively large with the impact of man-made constructions on estuarine within these bays from 1990 to 2000; （b） two bays, Haimen Bay and Hailingshan Bay, originally in the quasi-static equilibrium planform determined by the parabolic bay shape equation, have been unstable by the influence of coastal engineering; and （c） these 31 bays have different recession and accretion characters occuning in some bays and some segments. On the one hand, some bays totally exhibit accretion, but some bays show erosion on the whole. Shanwei Bay, Houmen Bay, Pinghai Bay and Yazhou Bay have the similar planforms, characterized by less accretion on the sheltering segment and bigger accretion on the transitional and tangential segments. On the other hand, different segments of some bays have two dissimilar evolvement characters. Dacheng Bay, Shenquan Bay, Hudong Bay, Wukan Bay, Fengjia Bay, Wuchang Bay, Lingshui Bay and Tufu Bay produce accretion on the tangential segment, erosion on the transitional segment and accretion on the sheltering segment. However, Guang＇ao Bay, Haimen Bay, Jinghai Bay, Sanya Bay（a）, Dajiao Bay, Hailingshan Bay, Hebei Bay, Fuhu Bay, Shuidong Bay, Wangcun Bay and Bomao Bay generate erosion on the tangential part, accretion on the transitional part and accretion on the sheltering part. It seems to imply some relations between headland-bay beach evolvement and controls on headland-bay beaches, which may possibly to classify headland-bay beach types and should be further studied.