Floodplain sediment from a 100-year-recurrence flood in 2005 of the Ping River in northern Thailand

Abstract

Abstract. The tropical storm, floodwater, and the floodplainsediment 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-km 2 drainage area of the Ping River upstream of the city of Chiang Mai was 867 m 3 s −1 (river-gage of height 4.93 m) and flow greater than 600 m 3 s −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 .The mass of dry sediment (32.4 kg m −2 ), measured over a 0.32-km 2 area of the floodplain is relatively high compared to reports from European and North American river floods. Average wet sediment thickness over the area was 3.3 cm. Sediment thicker than 8 cm covered 16 per cent of the area, and sediment thicker than 4 cm covered 44 per cent of the area. High suspended-sediment concentration in the floodwater, flow to the floodplain through a gap in the levee afforded by the mouth of a tributary stream as well as flow over levees, and floodwater depths of 1.2 m explain the relatively large amount of sediment in the measured area.

Changes in Climate Extremes over North Thailand, 1960–2099

“…The effects of urbanization that include the construction of major ring roads and changes in the Ping River bank and floodplains are blamed for causing more serious floods in recent years [21,[23][24][25]. Flooding and mudslides affected a large area in North Thailand, including Chiang Mai, Chiang Rai, Phayao, and Mae Hong Song Provinces [26]. The 2011 Chao Phraya River flood that caused $45 billion damage in Thailand highlights the difficulty of water management [27,28].…”

Ping River Palaeochannels: A Review of Evidence across Historical Literature, Archaeology and Geoscience

“…Overall, there are three mechanisms hypothesised to be involved in avulsion development in the Chiang Mai Basin -floods, earthquakes and human interference. These three factors are dominant fluvial drivers in the Chiang Mai Basin system -the Basin experiences frequent flooding (Wood & Ziegler, 2008;Ramdzan, 2016), experiences frequent low-to-moderate earthquakes (Fenton et al, 2003;Noisagool et al, 2016), and has a long history of channel engineering (Wyatt & Wichienkeeo, 1995;Penth, 2004;Lebel et al, 2010). Evidence of avulsion development is only available from Ping Hang research, which concluded that the Ping Hang avulsion was triggered by a flood (Velechovsky et al, 1987;Uttamo, 2004;Ng et al, 2015).…”

“…Though there is no record of this flood being related to the Ping Hang avulsion, the sheer magnitude of this flood led to some speculation that it may have triggered the avulsion (Velechovsky et al, 1987;Wood et al, 2004;Wood & Ziegler, 2008). This speculation is disputed by geochronological dating conducted later by Ng et al (2015).…”

River-Based Cage Aquaculture of Tilapia in Northern Thailand: Sustainability of Rearing and Business Practices

“…Evidence for the 2005 season showed that floods can significantly reduce profits of farms in vulnerable locations. The flood peaks on 14 August and 30 September, 2005, triggered by a tropical depression associated with Typhoon Damrey, it should be noted were the highest in the 1921-2007 flood history records and considered to recur once in a hundred year [30]. At the same time, the 2011 follow-up findings suggest floods are not a dominant reason in themselves for leaving fish farming.…”