Flash flood is the flood that is the short duration that can be the relativity that is the high peak discharge. The National Weather service (NWS) has adopted a more general definition of a flash flood “flash flood as a flood that follows the causative events ( excessive rain, dam or levee, etc within a few hours”(Hall, 1981, p. 1). The different between the regular flood and a flash flood is that flood is where the event have happen after 6 hours within the end of the causative events and the flash flood is within the 6 hours flowing the end of the the causative event ,(Hall, 1981). Flash flood is the most important danger national distaer in Washington state. According to Washington Military (2017) “Flood damage in Washington State exceeds damage by all other natural hazards”. For almost the last fifty year every count in Washington have received the Presidential Diaster declaration for flooding (Washington Military, 2017). Therefore, being preparation and resilience is necessary and used current research what will improve these methods (Bodoque et al., 2016; Hardy et al., 2016). This paper will first provide a background of the Puyallup and white river history, include two case study. Second, introduce scholarlay article about proarblictic flash flood forcastring and improving reslingence. Finally, I will summary the research and the finding.
Washington State is prone to Flash Flood for many reason and they happen in every season from spring to winter. Two important variables rainfall and snowpack. According to the Washington Military (2017) one reason is “ Rainfall on wet or frozen ground, before snowpack accumulation.” And the reason is “rainfall combined with the mealting of low elevation” (Washington Military, 2017). Melting snow pack on it own can cause flash flood (Washington Military, 2017). The Finally reason is Thunderstorms, especially during summer in Eastern Washington less frequently in Western Washington,
Melting glaciers on Mt Rainer are the number one cause for the Puyallup and White River (Pierce County, 2014). This most likely in Novbmer and March during Winter stomre. Melting from the 25 glacers go into the river quicky because of the short distance between the glacies and the rivers themselves. The Pulluyap River is flow the western smummit out of Puyallup and Tahoma Glaciers and the White River is 75miles from Emmons Glacier (Pierce County, 2014). Alpine glaciers during Pleistocene glaciation made the characteristic U-Shape vallege of Puyallup and White River ( Pierce County, 2014). Mt Rainer begin tall makes high slopes for the river water sheds. There is a great deal of sediment going downstream by way of the river to the lower water sheds. This due in large part to climate change . Temeperatiom are getting heigter and glaciers on Mt. Rainer are reatrating, which mean even more sefiment is flowing downstream (Pierce County, 2014). The melt carry debris such as rock, dirt, branches etc. Additionally, climate change contributes to frequent large storm, which make higher flow during flood.
In the Puyallup river village in particular flash flood is a hang probable for resiatant and the government. For example in 2009, people living in Orting where advistr to evacuation. Just last year, “ The national Weather Service has issues a flood warning for the Puyallup River.” (Rhatigan, 2017). The Puyallup river is about 45 miles long and flows through several south peirce county town, such as Sumner, Tacoma, and Fife ( Pierce County, 2014).
The white river is appendix 75 miles long and flows through Pierce and King county in cities including Buckley, Auburn and Pacific. In facts 75% of the river is pierce county. And 25% is in king county (Pierce County, 2014). The White River also form the country line pierce and King County. Similar to floods in 2009 around Orting, the white River flood too because of heavy rainfall. Over 50 years ago, the white River could handle downstream flows up to 20,00 cubic feet per second (Sistek, 2016) . In 2009, the river could handle 12,000 CFS (Sistek, 2016). Presently, the white River peck caoacity is only 5,000 cfs before it start to flood (Sistek, 2016). This dates shows that floods the white River would be a promble for the area in years to come.
Flood can happen anytime of year. However there are still away to preiected and prdpard for them.. Washiitgoton have a pattern of seasonal flash flood do to “ Heavy rainfall on wet or frozen ground, Rainfall combined with melting of the low-elevation snow pack, and Thunderstorms typically can cause a flash flood during the summer in Eastern Washington; on rare occasions, thunderstorms embedded in winter-like rainstorms cause flash floods in Western Washington.” ( Washington State Mililtey, 2017).
Two ways prepard for a flash flood through flash flood forcasting and improved of social resilience. Sience flash flooding is one of the most colsty and deady natural hardze across the United State. It is is exteramy important that public is inforamtin and education so they have a correct perecparted of the danger. (Bodoque et.al., 2016; Hardy et al, 2016).
According to the U.S. Army Corps of Engineers, in Seattle they talk about how the flood that if it can lower 8 miles that for the Puyallup River that is may not be able to qualify for the National Flood Insurance Program. “The river bed elevation of the Lower Puyallup River is expected to increase in future years from continued sediment aggradation, which will in turn cause increased flooding and greater EAD. Future EAD for 2017 and 2057 and the existing EAD are in constant FY2008 dollars. Over the 50-year period of analysis, the average value EAD is approximately $7,755,000. This value is referred to as the Expected Annual Damages (EAD)” (Pierce County, 2009). https://www.co.pierce.wa.us/ArchiveCenter/ViewFile/Item/893
On January 7-9, 2009 there was heavy rains that was up 3-5 up to 7.4 inches that was in the Pacific Northwest. The flood that can caused the major flooding that was on the serveral rivers and the several of the debris that will be flowing the river. “This flooding and debris flows caused $68 million in damages with fortunately no flooding related deaths” (National Weather Service,2009)
One of the research that was done what was done is method for the probabilistic flash flood. In a study by Hardly et al. (2016), “Flash flooding is one of the most costly and deadly natural hazards in the United State and across the globe” . The flash flood event is the one that is the meteorological event that can be the particular hydrological saturation. In the study is that “ Meteroriogically, it is but more importantly, the internsity and the movement of the rainfall to accurately depict the conditions the conditions of a flash flood event” (Hardly Et al. 2016, P.480). There method for forecasting flash flood that hardy et al. (2016) create is probabilistic flash flood forecasting (PFFF). The methods identify “basic skcale and lead time for flash flood prediction” (p.484). The first step is to be able to calcularting a probavility of exceedance(Hardly Et al. 2016). The second is to be able quantuattive precipitation forecast(qpf) (Hardly Et al. 2016) .The final step is to have the process to create a PFFF to be able to multipt the hudrolic model output(Hardly Et al. 2016). Metorology can used this method to account for locitonal uncerationes and to know when a flash flood is coming.
Another piece of research by Bodoque et al. (2016). Study the how to improvement of resilience of Urban areas. As previsity mentioned, the cost of flash flood is enormous for the govemernt and the towns in king and pierce country. Bodoque et al. (2016). Discuss how flash flood can also have higher mortality. They address social perception and it role in flash flood risk management. The first thing that they recommed is to update demographic information the people who live areas that flash flood can happen (Bodoque et al. ,2016). The second thing that they find is people think they know what to do in a flood but, they don’t know (Bodoque et al. ,2016) . The author recommend that the peoples flase understanding be taking into account when we tell people about the plan for flash flood (Bodoque et al. ,2016). When risk perception and aware are low flood plan as useful.
Based on the research, we need to asses people’s awareness who live near the Puyallup and White River and maybe implement an awareness program. There is already a flood plan in places for these areas. For example, instruction how to prepare for flood can be find on the city of Puyallup website. However, peoples who have live near the river for all time may falsely assume that they are prepared as Bodoque et al. (2016) shows. There for we should conduct awareness survey in these areas to reduce cost and saves lives. When be able to be prepard for flash flood that the better chance of living and be