‘Dam’n Floods

December 2016: San Francisco – Kary, who I shared an Uber ride with, thinks that Pineapple Express is a funny name for a storm.

November 2016: Vietnam – Ha Ting, Quang Tri and Quang Binh provinces that experienced rainfall in October, are hit by another wave of heavy rainfall events. Tens of thousands of people displaced.

October 2016: Argentina – Long-term flooding in Buenos Aires affects rural and farming areas. Persistent rainfall leads to an overflowing Quinto River. Agricultural emergency declared.

July 2016: China – Yangtze River overflows. Around 40,000 houses destroyed. More than 1.5 million hectares of cropland damaged.

June 2016: Texas – Heavy rain has increased river levels. President Declares Disaster for 12 counties.

A common thread in all these events is that the floods lasted for more than 30 days and are associated with repeated rainfall into the region. These are colloquially called long duration floods. Understanding the causes of these types of floods and using that information for managing water infrastructure is a recent area of research.

Nasser Najibi is working in this field and has recently published an article in Advances in Water Resources Journal on the atmospheric teleconnections of long duration floods. Large dams along the main stem of the Missouri River Basin are selected for this investigation. For each dam, we differentiate long duration floods from short duration floods and identify what hydrological, climatological and atmospheric conditions cause the long duration floods. Nasser derived a precursor index that shows an incipient condition for long duration floods. There is an organized atmospheric structure (spatial arrangement of high-pressure nad low-pressure areas) that draws the storm tracks repeatedly into the region causing recurrent rainfall events. These repeated waves of rainfall events fill up the dams and cause river overflows. We are now developing reservoir operation models using this prognostic information for managing flood hazards better . More information can be found in the journal article. We welcome any comments.

Oh, and Pineapple Express is not just a 2008 comedy film or a funny name for a storm. It is also a common term for a strong and persistent flow of atmospheric moisture that causes heavy precipitation in mid-latitudes. Its discovery initiated this new field of climate-informed flood risk research.