Man Against the Sea: Natural and Anthropogenic Factors in the Changing Morphology of Harngzhou Bay, circa 1000-1800

Abstract

Abstract Inner Harngzhou Bay, on the east coast of China at approximately 30 degrees N, is an unstable macrotidal estuarine system whose geographical configuration has altered dramatically over the last thousand years. In particular, the mouth of the Qiartarng river has shifted twice: (1) in 1620 from a southern debouchement just to the north of Mount Kan to a central or mid-bay debouchement south of mount Herzhuang, and (2) in 1692-5 from this central debouchement to approximately its present northern exit. A thousand years ago there was an approximate balance between the deposition of sediments, mostly brought in by the tides from the mouth of the Yarngzii immediately to the north, and their removal by river flow, especially at periods of peak discharge, in conjunction with ebb tides. Human intervention made a major contribution to disrupting this equilibrium by the building of sea-walls, the diversion of rivers, and the reduction of peak discharge, in part by storing water in irrigation systems. The shift of the Yellow River to a predominantly southern course after 1194, and especially the increased discharge of fine-grain sediment at its sea-mouth as the result of hydraulic engineering in 1578-9, also played a part, by increasing the quantity of fine-grain sediments transported southwards down the coast. The committment of both local society and imperial government to complex and costly hydraulic systems in this area created forms of what may be termed 'technological lock-in', in other words a foreclosing of other options on the future use of labour, resources and administrative inputs, though release from the 'lock-in' could also sometimes occur as the result of shifts in the patterns of sediment deposition and erosion that were favourable to human economic interests. The present paper summarises and interprets previous work on the hydrology and hydraulics of this area, presents a preliminary reconstruction of the geographical pattern of change based on historical maps and documents, and outlines some of the analytical problems that will need to be addressed in the future. It also shows that, under certain circumstances, geomorphological change, partly anthropogenic in origin, can affect human social and economic life over relatively short periods (typically tens to hundreds of years). The conclusion is that long-term economic history without environmental history is, at best, lopsided and, at worst, misleading.