l820 Flood Insurance Maps Evaluating Point Park Reference elevations Base Levee
ID: 105198 • Letter: L
Question
l820 Flood Insurance Maps Evaluating Point Park Reference elevations Base Levee 840 ft River 3 ft below flood plain 100-yr flood +7 ft 500-yr flood +12 ft North STAFF TRANSECT B 870 South GAGE 870 865 HICKORY 865 ESTATES 860 860 RIVERSIDE POINT PAR 855 S 855 850 850 845 845 AVERAGE 840 840 WATER LEVEL 835 835 3500 3000 2000 1500 2500 1000 500 Palouse Clearwater Distance, in feet River River (1) On the staff gage, mark the elevations of the 100-year flood, and the 500-year flood. (2) Mark on the profile (which represents the land surface) those two elevations. (3) Label the modern (active) flood plain. Label the higher river terrace. (4) Draw arrows to show where you think a typical 10-year flood might reach (5) lain writing: Where is Point Park relative to the 100-year & 500-year flood elevations? inExplanation / Answer
1. The 100 year flood 7 ft above the base level and 500 year flood is 12 ft above the base line. The base line is at 840 ft.
So 100 year flood level = 840+7 = 847 ft.
500 year flood level = 840+12 = 852 ft
2. Draw a horizontal line at 847 and 852 on the graph. Where it touches the graph will be the profile of the land surface at those two elevations.
3. Mordern active flood plain is at 840ft since the river is 3 ft below this level.
4. Assuming the increase in flood level is uniform then using 7ft in 100 years we get 0.7 ft and using 12ft in 500 years we get 0.24 ft. So its between 0.24-0.7 ft in coming 10 years.
5.Point park will be just above the for 100 years food elevations but it will be submerged in water in 500 years flood elevation since its height is about 852 ft.
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