Flooding risks change due to land use and precipitation change in Northern Taiwan

According to the records, an average of 5.3 typhoons hit Taiwan each year over last decade. Typhoon Morakot in 2009 was considered the most severe typhoon, which caused huge damage in Taiwan, including 677 casualty and roughly NT$ 110 billion ($3.3 billion USD) in economic loss. More and more researches documented that typhoon intensity will increase with climate change in western North Pacific region. It will induce the more severe natural disasters, such as flooding, landslide, and water resources risks in Taiwan in the future. Most research focused on the disaster impact assessment in climate change and was assumed that the land use are unchanged in the future. On the other hand, land use changes is another key reason for increasing the hazard risks. Therefore, this study tries to build a land use change model to simulate the land use spatial distribution, and discuss whether the extreme precipitation or the land use change is the major factor to increase flooding risks in Taoyuan City, northern Taiwan in the future.

This study applied that Markov chain to project the land use demand in 2036 and used the binary logits regression to establish the land use change probability model to allocate the land use spatial distribution in the future. Then, there are two different precipitation intensities used and integrated the allocated land use to evaluate the risks of flooding in 2036.

We successfully established land use spatial allocation model, and linked the allocated results to disaster impact assessment. Assessment results showed that land use change slightly increases the flooding risks; but extreme precipitation induces more severe flooding risks than land use change. Our results point out that extreme precipitation will induce the more severe flooding risks than land use. In addition, the restricted land development policy could efficiently reduce the flooding risks. If government implement climate change adaptation activities with land use management policies at the same time would possibly reduce the climate change disaster impact in the future.