Question 1. You can use the 10-year, 3-hour return period maps as a rule-of-thumb value of rainfall required to produce flooding in the absence of other information. Determine the 10-year, 3-hour return period value for your location.
 

Ardmore is roughly 2/5 (.4) of the way between the 3.5 and 4.0 inch contour. Take the difference between the contours (4.0 - 3.5 =.5 inches) and multiply it by the distance calculated for Ardmore: .4 x .5 = .2. Add the result to the lower contour value (3.5 + .2 = 3.7), this is the 10-year, 3-hour return period value for Ardmore, Oklahoma.