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NASA Global Near-Real-Time and Research Precipitation Products for Flood Monitoring, Modeling, Assessment, and Research
Published in Saeid Eslamian, Faezeh Eslamian, Flood Handbook, 2022
Zhong Liu, Dana Ostrenga, Andrey Savtchenko, William Teng, Bruce Vollmer, Jennifer Wei, D. Meyer
The data latencies (from satellite acquisition) for near-real-time TMPA and IMERG are approximately eight and four hours, separately. Flash floods usually occur within six hours after a heavy rainfall event, depending on rainfall intensity, duration, and size of the watershed. Apparently, the latency of near-real-time TMPA has exceeded this time period for flash floods and may not be suitable for smaller-scale flash flood operation, compared to ground radars that can provide observations much faster when available. Improvements on data latency are still needed for satellite-based multi-satellite and multi-sensor precipitation products. On the other hand, the latency of near-real-time IMERG is improved and significantly shorter than TMPA and could be used in some flash flood applications. For other large-scale floods, both near-real-time TMPA and IMERG are suitable (e.g., Wu et al., 2014).
Floods: Riverine
Published in Yeqiao Wang, Wetlands and Habitats, 2020
William Saunders, Alison MacNeil, Edward Capone
River flooding occurs at different rates for different locations. Slow and steady river rises to flood thresholds commonly occur on larger rivers that have more significant drainage areas and wider channels with greater assimilative capacity. Conversely, more rapid flooding events, or “flash floods,” generally occur on smaller rivers that drain smaller watersheds. Other characteristics of locations that are prone to frequent flash flooding include (a) steeply sloping upstream river channels and (b) a high percentage of low-permeable soils in the contributing watershed. Flash floods are common in mountainous regions, where exposed rock formations inhibit the infiltration of rainfall into the soil and tributary streambeds are steep. Flash floods are also common in urban areas, where much of the land cover is developed with impermeable surfaces (e.g., roadways, parking lots, and roof structures).
Changing Flood Risk – A Re-insurer’s Viewpoint
Published in Zbigniew W. Kundzewicz, Changes in Flood Risk in Europe, 2019
Flash floods are caused by high-intensity rainfall, often occurring over a very small area and typically in conjunction with thunderstorms, during which the precipitation rate exceeds the infiltration rate and the drainage and storage capacities at the site where it occurs. The water rapidly converges in the receiving streams, thus leading to swiftly rising water levels and flood waves. Where the terrain is flat or does not slope sufficiently, water accumulates on the surface, but local inundation can reach considerable depths - for instance in depressions in the landscape which may not even be noticeable to the eye. On a sloping terrain, the water gushes downwards, sometimes at high velocity and with extreme destructive power. The intensity of the flood is increased by floating matter and sediment, ground and channel erosion, and the undermining of building foundations.
The impact of weather extremes on urban resilience to hydro-climate hazards: a Singapore case study
Published in International Journal of Water Resources Development, 2018
The second instance of extreme weather pertains to the significant and increased frequency of reported flash flood events occurring in the city-state over the past 30 years, most notably with two June 2010 flood events in the popular shopping district of Orchard Road. These floods occurred from a combination of short-duration, very intense rainstorms over the Orchard Road area, and a partially blocked culvert that restricted drainage from the inundated area. While no deaths or injuries were reported, the knee-deep flood waters resulted in S$ 23 million (US$ 17 million) of insurance claims (Chow, Cheong, & Ho, 2016). While the likelihood of urban flash-floods locally is high given the large degree of impermeable surface cover, combined with low elevation, tide levels, and coastal location, significant increases in (1) the measured intensity of rainfall events and (2) the recorded frequency of large rainfall events (over 70 mm/h) in 1980–2010 appear to be a causative factor in this recent prevalence of flash floods (Ministry of the Environment & Water Resources, 2012; Beck et al., 2015). In other words, a trend of more frequent and intense rainfall events in recent years can overwhelm existing drainage infrastructure not designed to anticipate increases in extreme precipitation. Ssince 2013 PUB has embarked on a series of drainage improvement projects to improve the overall urban resilience to extreme-precipitation-driven flash floods. These measures include installation of water detention tanks, additional diversion canals, the widening or deepening of existing canal drainage networks, and the replacement of drain inlets with gratings designed to reduce blockage or choking of inlets from debris (AsiaOne, 2013).
Assessment of flood susceptibility in coastal peri-urban areas: an alternative MCDA approach for ungauged catchments
Published in Urban Water Journal, 2022
Vassiliki Terezinha Galvão Boulomytis, Antonio Carlos Zuffo, Monzur Alam Imteaz
Flash floods occur following intense rainfall in short periods of time. As the basin is not gauged, it was not possible to use the 24 h design rainfall for the MCDA analysis, which would determine its effect on the peak discharge at the sub-basin outlets. Hence, a parallel analysis of the correlation of annual and daily rainfalls was carried out, both for the maximum registered values and for the average values in the period, in order to confirm the suitability of using the average maximum annual rainfall for the MCDA model (Figure 6).