Determination of Critical Rainfall Boundary for Landslide Warning

Abstract

Land slide is one of the natural disasters that cause a lot of damage in many parts of the world. Thailand also affected and more severe in every time especially northern and southern parts due to area geology is mountain with high slope cause an occasion of landslides. Also rapid increase of economic and population growth push people to migrate into risk area of landslide including human activities or career on the slope make opportunity to increase landslides This research is study about the relationship between rainfall and landslide in Thailand mountainous area. We set up rainfall crisis and develop warning threshold using past evident of landslide and rainfall history. From 1970 to 2010 had 169 times of landslides and the rainfall history from Meteorological Department. The important part is how to set up rainfall duration to match with landslide by consider to rainfall which is make a slop to fall as landslide to set up rainfall crisis and warning criteria. ง From the result, the appropriate duration was 4 days for Northern and Southern Thailand. The critical rainfall and landslide warning threshold can be illustrated by daily rainfall and 3 days antecedent rainfall relationship. However, both area can be divided into 2 parts by considering of critical rainfall boundary. First is upper boundary where landslide was triggered by heavy rainfall and the second is lower boundary where landslide can be occurred by rainfall lower than upper boundary. .