Flood Assessment

1179 Words Oct 8th, 2012 5 Pages
The purpose of this report is to geologically evaluate the potential hazards for flooding in Hazard City. This report will include a detailed historic and extrapolated Stream Gauge Data Worksheet, as well as a graph of the Discharge Frequency Curve expected on Clearwater River. The report will provide Hazard city with my scientific analysis, conclusions, and provide recommendations concerning potential flood damages.
The methodology used was to utilize the Recurrence Interval formula (R) = (N+1)/M, to determine the recurrence interval and magnitude of historical floods provided on the Stream Gauge Data of Peak Flood Discharges on Clearwater River in Hazard City. Also, I reviewed the flood insurance map to
…show more content…
Another reason for this scientific assumption is that the Downtown area, which is inundated with impervious covered surfaces, will produce runoff, especially in the event of a flash flood, and will meet in this same area along Clearwater River near Ralston (Keller, 2008, p. 269).
Information that was used to develop my conclusions were relative to the history of Clearwater River such as the average normal discharge of 40,000cfs, the fact that the river can accommodate 55,000cfs before flooding will occur, and that with every increase of 2600cfs the river rises one foot. For example, this information helped to determine that four of the thirteen noted Peak Flood Discharges listed on the worksheet were not at flood stage as the river is able to accommodate discharges less than 55,000cfs. However, nine of the thirteen Peak Flood Discharges listed on the worksheet were at flood stage or drastically above; with the maximum rise of 17.77 feet above and a discharge rate of 101,200cfs. The average discharge rate of the top three noted floods per information on the Stream Gauge Data of Peak Flow Discharges is 93,613cfs, which is resourceful later in determining the extrapolated 75-year flood.
1. What is the recurrence interval of floods in Hazard City?
The average recurrence interval of floods in Hazard City is 1 in 7.14 years; with an average flood discharge rate of 78,885cfs and a magnitude of 7. The typical flood in Hazard City