APPLICATION OF PALAEOFLOOD SEDIMENTOLOGY TO IDENTIFY CHANGES TO THE FLUVIAL ENVIRONMENTS AND TO RECONSTRUCT PEAK DISCHARGES IN THE UPPER PING RIVER, CHIANGMAI

Abstract

This thesis is an exploratory study to extract past flood signals from floodplain sedimentary records at Ban Pa Po (BPP) and Ban Pa Ngae (BPN) through using sedimentology studies, specifically grain size parameters and organic matter content, and historical archives of the Ping River catchment. Grain size properties of the identified flood signals were used as a proxy for annual peak discharge at P1 in Chiang Mai with the aim of producing a reliable method to lengthen peak discharge records of large flood events in lower fluvial reaches. To obtain long-term flood magnitude, flood signals were first identified from sedimentary records through developing conceptual models of the past fluvial depositional environments at BPP and BPN. With an understanding of past sedimentation processes, the normalised grain size parameters of the identified flood signals from individual and combined sites can then be related to peak discharge.