Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 12 4 2008 10.5194/hess-12-959-2008 http://www.hydrol-earth-syst-sci.net/12/959/2008/ http://www.hydrol-earth-syst-sci.net/12/959/2008/hess-12-959-2008.html http://www.hydrol-earth-syst-sci.net/12/959/2008/hess-12-959-2008.pdf 959 973 2008-07-11 Floodplain sediment from a 100-year-recurrence flood in 2005 of the Ping River in northern Thailand S. H. Wood swood@boisestate.edu A. D. Ziegler Department of Geosciences, Boise State University, Boise, Idaho 83702 USA Geography Department, University of Hawaii, Honolulu, Hawaii 96822, USA Geography, National University of Singapore, Singapore The tropical storm, floodwater, and the floodplain-sediment layer of a 100-year recurrence flood are examined to better understand characteristics of large monsoon floods on medium-sized rivers in northern Thailand. Storms producing large floods in northern Thailand occur early or late in the summer rainy season (May–October). These storms are associated with tropical depressions evolving from typhoons in the South China Sea that travel westward across the Indochina Peninsula. In late September, 2005, the tropical depression from Typhoon Damrey swept across northern Thailand delivering 100–200 mm/day at stations in mountainous areas. Peak flow from the 6355-km2 drainage area of the Ping River upstream of the city of Chiang Mai was 867 m3s−1 (river-gage of height 4.93 m) and flow greater than 600 m3s−1 lasted for 2.5 days. Parts of the city of Chiang Mai and some parts of the floodplain in the intermontane Chiang Mai basin were flooded up to 1-km distant from the main channel. Suspended-sediment concentrations in the floodwater were measured and estimated to be 1000–1300 mg l−1. 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