Property slope

I need to determine how steeply sloped a piece of land is. To accomplish this I would like someone to develop an algorithm to score each property, then apply this algorithm to each property in the desired counties. Deliverables: ( a ) a spread sheet (one for each county) that provides the address, lat/lon, and metrics for the slope of the property at each address (where the lot size is 1 acre or more). Below is an example of the format of the desired spread sheet (see attached) Note, conceptually, the average slope is the slope (feet rise / feet run) per an arbitrary unit area ( dA) times the area of the property (this calculation is left to you to work out). The “other metric” is some other metric that you think would be helpful. Conceptually, the area encompassed by dA is bounded on either of two sides by contour lines (if averaging occurs over multiple lines, dips and rises could be averaged out), the other boundaries are determined by you. Note, some addresses include more than on lot. All lots should be analyzed for each address. Note, these data should exclude addresses that are less than 1 acre in total. Note, please use the highest resolution contour data available for each plat. In many cases this is 4 or 5 foot contour data. In other cases it is 10 foot contour data. ( b ) a map that includes the plats such that I can zoom into a particular address and see the plat and slope metrics. This map can be setup in Google maps, Google Earth, World Wind, etc. Background In particular, I would like to buy a house or lot (of 1 acre or more) in Virginia (somewhere in the Shenandoah, Warren, Clarke and Frederick (including Winchester and Stephen cities) Counties) on a property that is not too steep. The contour and plat data (including area of each property) are available, for example, on the GIS site for each county. An address list ([login to view URL]) is readily available on the Virginia GIS site. The “other metric” could describe the uniformity of the property, for example. For example, a 3 acre lot having 2 acres of flat land and 1 acre that has a 60% slope, the average of 20% is misleading. That is, the lot has a nice 2 acre spot for a house and garden. Whereas a 3 acre lot with a uniform 20% slope is less desirable. Please note that at the completion of the project, you own your work, algorithm, data and maps (with the exception of the deliverables which you share with me). You may disseminate your work, algorithm, data and maps (including the deliverables above) as you wish and apply your work to future projects as you wish. For example, you can sell it to some other real estate company that might be interested.