Flash Flood
A flash flood is the kind of flood that is of the shortest duration that can be the relatively that is in the high peak discharge. The National Weather Service (NWS) has adopted a more general definition of a flash flood; a “flash flood is a flood that follows the causative events (excessive rain, dam or levee, etc) within a few hours” (Hall, 1981, p. 1). The difference between the regular flood and a flash flood is that a regular flood is where the event has happened after 6 hours within the end of the causative events. and the flash flood is within the 6 hours following the end of the causative event (Hall, 1981, p.#). A flash flood is the most important, dangerous natural disaster in Washington state. According to the Washington Military Department (2017), “Flood damage in Washington State exceeds damage by all other natural hazards” (p. or para. #). For almost the last fifty years, every county in Washington has received the Presidential Disaster Declaration for flooding (Washington, 2017, p. or para. #). Therefore, being prepared and resilient is necessary, and using current research is what will improve these methods (Baroque, et al., 2016, p. #; Hardy, et al., 2016, p.#). This paper will, first, provide a background of the Puyallup and White Rivers’ histories, including two case studies. Second, it will introduce a scholarly article about probabilistic flash flood forecasting and improving resplendence. Finally, I will summarize the research and the findings.
Washington State is prone to flash floods for many reasons, and they happen in every season from spring to winter. Two important variables are rainfall and snowpack. According to the Washington Military Department (2017), one reason for flooding is “Rainfall on wet or frozen ground, before snowpack accumulation,” and another reason is “rainfall combined with the melting of low elevation words missing????” (p. or para. #). Melting snow pack on its own can cause flash flood (Washington, 2017, p. or para. #). The final reason is Thunderstorms, especially during the summer in Eastern Washington, but they occur less frequently in Western Washington,
Melting glaciers on Mt. Rainer are the number one cause for flooding on the Puyallup and White Rivers (Pierce County, 2014, p. or para. #). This occurs most likely in November and March during the Winter storms. Melting snow from the 25 glaciers go into the rivers quickly because of the short distance between the glaciers and the rivers themselves. The Puyallup River is flowing from the western summit out of the Puyallup and Tahoma Glaciers, and the White River is 75 miles from Emmons Glacier (Pierce County, 2014, p. or para. #). Alpine glaciers, during Pleistocene glaciation, made the characteristic U-shape valley of Puyallup and White River (Pierce County, 2014, p. or para. #). Mt. Rainer, being tall, makes high slopes for the rivers’ watersheds. There is a great deal of sediment going downstream by way of the rivers to the lower watersheds. This due in large part to climate change, temperatures that are getting higher, and glaciers on Mt. Rainer that are reiterating, which means even more sediment is flowing downstream (Pierce County, 2014, p. or para. #). The snowmelt carries debris, such as rocks, dirt, branches, etc. Additionally, climate change contributes to frequent large storms, which makes higher water flows during a flood.
Puyallup River
In the Puyallup River valley, flash flooding is a huge problem for resistant and the government. For example, in 2009, people living in Orting, were advised to evacuate. Just last year, 2017, “The National Weather Service has issued a flood warning for the Puyallup River” (Rhatigan, 2017, p. or para. #). The Puyallup River is about 45 miles long and flows through several South Pierce County towns, such as Sumner, Tacoma, and Fife (Pierce County, 2014, p. or para. #).
White River
The White River is approximately 75 miles long and flows through Pierce and King Counties, through cities including Buckley, Auburn and Pacific. In fact, 75% of the river is in Pierce County. And 25% is in king county (Pierce County, 2014, p. or para. #). The White River also forms the county line between Pierce and King Counties. 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 capacity is only 5,000 cfs before it starts to flood (Sistek, 2016). This dates shows that floods the white River would be a problem for the area in years to come.
Flooding can happen any time of year. However, there are still ways to predict and prepare for them. Washington has a pattern of seasonal flash floods due 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, 2017, p. or para. #).
Two ways to prepare for a flash flood are through flash flood forecasting and improvement of social resilience. Since, flash flooding is one of the most costly and deadly natural hazards across the United States, it is extremely important that the public is informed and educated so they have a correct preparedness of the danger. (Bodoque, et.al., 2016, p. #; Hardy, et al, 2016, p. #).
According to the U.S. Army Corps of Engineers, in Seattle, WA, they talk about how the flooding that if it can in the lower 8 miles that for of the Puyallup River that is may not be able to qualify for the National Flood Insurance Program if it does not participate in flood risk management;
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, p. or para. #).
With the Puyallup River basin, it can be still experience the continued with the flood damage that can have a huge impact on the local economy and that the flash flooding can threaten the lives of the town peoples that live near the Puyallup River.
On January 7-9, 2009, there were heavy rains that was up measured from 3-5 inches up to 7.4 inches that was in the Pacific Northwest. The flooding that can caused the major flooding that was on the several rivers, and the several of the danger was from the debris that will be flowing the river. The National Weather Service (2009) reported, “This flooding and debris flows caused $68 million in damages with fortunately no flooding related deaths” (p. or para. #)
One of the research studies that was done what was done is for a method for the probabilistic flash flood. In a study by Hardy, et al. (2016), “Flash flooding is one of the most costly and deadly natural hazards in the United States and across the globe” (p. or para. #). The flash flood event is the one event that is the meteorological event that can because of the hydrological saturation. In the study, is that Hardy, et al. (2016) reported, “Meteorologically, it is but more importantly, the intensity and the movement of the rainfall to accurately depict the conditions the conditions of a flash flood event” (p. 480). The method for forecasting flash floods that Hardy, et al. (2016) created is the Probabilistic Flash Flood Forecasting (PFFF), and the method identifies “basic scale and lead time for flash flood prediction” (p.484). The first step is to be able to calculate a probability of exceedance (Hardy, et al., 2016, p. or para. #). The second is to be able to develop a quantitative precipitation forecast (qpf) (Hardy, et al., 2016, p. or para. #). The final step is to have the process to create a PFFF to be able to multiply the hydraulic model output (Hardy, et al., 2016, p. or para. #). Meteorology can use this method to account for locational uncertainness and to know when a flash flood is coming.
Another piece of research was done by Bodoque, et al. (2016). They studied the how-to improvement of resilience of urban areas. As previously mentioned, the cost of flash flood damage is enormous for both the government and the towns in King and Pierce Counties. Bodoque, et al. (2016) discussed how flash floods can also have a higher mortality rate. They address social perception and its role in flash flood risk management. The first thing that they recommend is to update demographic information about the people who live in areas where flash flooding can happen (Bodoque, et al., 2016, p. or para. #). The second thing that they found was that people think they know what to do in a flood, but they really don’t know (Bodoque, et al., 2016, p. or para. #). The author recommends that the people’s false understanding be taken into account when officials tell people about the plans for flash flooding risk management (Bodoque, et al., 2016, p. or para. #). When risk perception and awareness are low, flood plans are not as useful.
Based on the research, the county and state governments need to assess people’s awareness who live near the Puyallup and White Rivers and to maybe implement an awareness program. There is already a flood plan in place for these areas. For example, instructions about how to prepare for floods can be find on the City of Puyallup’s website. However, people who have lived near the river for a long time may falsely assume that they are prepared as Bodoque, et al. (2016) showed. Therefore, county and state officials should conduct awareness surveys in these areas to reduce damage costs and to save lives. When a person is able to be prepared for flash flooding, that the they have a better chance of living, and cities should be able to have a warning system in place. It may be too late for a person to be able to get out of a flash flood when they have no warning, because they may not be able to know that there is one coming, and with preparation, they can get the help that they