Annual Runoff
Obtained an annual runoff coverage from USGS
Set of contour lines converted to a point coverage
Interpolated a surface from the point coverage
Annual runoff for Marcus Hook = 20 in.
Notes:
The first thing I looked at was determining the annual runoff. I started with an annual runoff coverage I obtained from the USGS website. This coverage was constructing using data from the years 1951-1980, and it is a set of contour lines. The problem is that you cannot interpolate a surface from a set of lines. So I essentially worked backwards and created a point coverage from the set of lines. I was then able to interpolate a surface from these points. As a side note, I have created a generic Avenue script to accomplish this task which anyone can use. I made a runoff grid for the entire United States with a cell size of 1 km and a smaller grid for Pennsylvania with a cell size of 500 m. From the Pennsylvania grid, I obtained to the 20 in. runoff value.