Environment Problems in the Coastal Zone
3 Environment Problems in the Coastal Zone Chairs: Hideo Sekiguchi and Sanit Aksornkoae 3.1 Coastal Characteristics and Changes in Coastal Features Yoshiki Saito Geological Survey of Japan, AIST, Central 7, Higashi 1-1-1, Tsukuba, Ibaraki, 305 8567 Japan Understanding coastal dynamics and natural history is important in developing a better understanding of natural systems and human impacts in coastal zones. This chapter outlines the characteristics of sedimentary environments in coastal zones which must be understood in order to manage and preserve coastal environments. 3.1.1 Coastal Classification, Shoreline Migration, and Controlling Factors The world’s coastal environments and topography are classified into two types on the basis of the changes which occurred during the Holocene when they were particularly influenced by millennial-scale sea-level changes. Transgres- sive coastal environments, where shorelines migrate landward, are characterized by barriers, estuaries, and drowned valleys (Boyd et al., 1992). Regressive coastal environments, where shorelines migrated seaward, consist of deltas, strand plains, and chenier plains (Fig. 3.1.1). Thus regressive shorelines at river mouths are called deltas, while trans- gressive shorelines at river mouths are called estuaries. The latter consist of drowned, incised valleys. In regressive environments, coastal lagoons sepa- rated from the open ocean by barriers are well developed alongshore, whereas estuaries cross the general coastline. A strand plain is a coastal system that develops along a wave-dominated coast; it is characterized by beach ridges, a N. Mimura (ed.), Asia-Pacific Coasts and Their Management: States of Environment. 65 © Springer 2008 66 H. Sekiguchi and S. Aksornkoae FIG.
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