Geomorphological Responses in a Dynamic Environment: How Landforms Interact with Human Activities in Taiwan

Abstract

This chapter attempts to assess how frequent earthquakes and seasonal typhoons that strike often and with significant consequences shape landslide, river channel change and coastal change in the dynamic environment of Taiwan, a small subtropical island. The impacts and consequences of earthquakes and typhoons, mainly manifested geomorphologically in landslides and associated features, are made even more brutally detrimental due to the dense population distribution and related human activities of Taiwan. Sediment yields from river catchments may be indicators of landslide activity, along with river channel change and several other geomorphological features. Sediment deposition in the lowlands, where there are diverse land uses and economic activities exacerbates damage caused by such processes. Sediments may accumulate at unprecedented rates (e.g. Typhoon Minudle in 2005 and Typhoon Morakot in 2009 which resulted in sediment accumulation in river channels of 30 and 60 m respectively). Seasonal dynamics and unpredictability of sediment yields manifest also in coastal geomorphology, especially because settlement and economic activities are concentrated in these regions in Taiwan resulting in both urban and rural development challenges. All these phenomena are considered as integral to the dynamics of the environmental system of Taiwan. Landslides, river channel changes, and coastal changes represent three sides of an environmental triangle that require detailed study and understanding if such challenges are to be mitigated. Remote sensing imagery, in particular aerial photos and field observation records are employed in a series of case studies to demonstrate how the dynamic Taiwan environment can better be understood in relation to the geomorphological processes and features including landslides, river channel and coastal change. Limitations to the use of marginal land and the adoption of buffer zones to mitigate geohazards are proposed.