Topography in Land Development
Land development considerations
One of the key considerations in land development is the topographic condition of the land. The specific area we’ll look at today is land surface elevations and contours to gain understanding about the shape and form of a parcel. Also, considerations regarding what should be done to manage project elevation and countour differences for a better layout and yield.
Everyone understands that elevation refers to how high something rises above a given reference point. In surveying and mapping the reference point is called a datum. In real estate the datum you will see on topographic maps is usually MSL (mean sea level). MSL is accepted worldwide as a standard datum or reference point from which elevation is measured and real estate topographic maps typically use it.
Know your datum:
Not all datum are the same however. A comparative example would be the above referenced topographic map that uses mean sea level as the datum, compared to how Mt. Rainier, the tallest mountain in Washington State is measured. Mt. Rainier is measured at 14,411 feet, but that is not above mean sea level. A different datum is used to measure this mountain - in this case it’s highest point above it’s nearest low point. So we see here that Mt Rainier is essentially measured against itself - it’s own low and high point.
That’s enough datum drain for now. Just realize if your are looking at an elevation you need to understand what datum the measurement is being based on. The easiest and fastest way to do this is to look at the map legend.
Topographic maps will show contour lines. There are four different types of contour lines and the one we are interested in for real estate represents joined points of equal elevation above mean sea level. The spacing between the contour lines will show distance as defined on the scale of measurement, i.e. 1” = x ft.
Can be a friend or enemy for the developer. The good news is that they are clearly defined as a topographic feature so a lot of the guess work about what can be done around them is clear, even for a novice. The substrate of a cliff needs to be considered. If it’s basalt rock as an example it will probably be relatively stable. If it is some sort of soil and rock structure bound by clay it could be stable in dry conditions and unstable in wet, thus shedding debris (tallus) below.
I don't like property that has been filled unless I have done it myself. This is because if someone else did it I don’t necessarily know where the fill came from. Dumping toxic dirt is illegal if done incorrectly and expensive if done legally, so there have been many instances of guys illegally transporting soil from a contaminated sites to some guy who wants “free fill”. Soil testing is essential when looking at a piece that has been filled and don’t count on the seller to disclose it..
Fill can also be used to flatten sensitive areas like wetlands. This is not only illegal in many cases but can also change the surface water runoff characteristics of a property. Doing this can also affect the hydrology of surrounding properties. Filling in real estate can cause code violations and legal liability in a variety of areas.
Like everything else in land, there are always exceptions - like in Florida. As an entire state, Florida averages about a 100 ft. MSL in elevation. The highest point in the entire state is only 345’. Therefore, in Florida almost every project uses fill to elevate homesites and take out the low points as a matter of approved permitting. Note however, that the developer is doing the filling with soil from known and approved sources.
Gullies can be a real problem, especially if the are irregular. They can also cause a developer to have to bridge the gap for road infrastructure which is a huge cost and general pain in the rear. I did a bridge across a gully with a salmon stream at the bottom. It cost about $500,000 for a mere 38’ span! When dealing with radical elevation changes, look for alternative access points. Some guy on the other side might be willing to sell an access easement.
This is what every seller emphasizes on a property for sale since it implies that the land is entirely useable. Sometimes that is the case, but not always. I love it when you see a listing that says “mostly level” since it hardly ever is when you actually get on-site. In any case, like everyone else I prefer a flatter piece as a general rule.
Bear in mind that flat topography holds it’s own set of challenges. For instance, surface water runoff and drainage in general. Sheeting water has to go somewhere and a qualified Geotech consultant is generally needed for hydrology considerations. Also consider that when water remains on flat land it is generally absorbed by the soil until saturation occurs. That can cause seasonal softening of the soil from wet spots or wetlands.
Although none of my Florida projects have been on rolling terrain (since there isn’t any), almost all of my projects in the Pacific Northwest have been. An advantage to rolling terrain is that runoff tends to be directed to known points. The variances in elevation can provide some nice territorial views if the developer considers each and every homesite position in the design process.
I love slopes too, as long as they are not overly radical. I did a plat onetime in the Cascade foothills. There was a flat bench at the top with a slope downward to the north property line. It was a couple of hundred acres in size and each roof top of the home below left the higher one with unobstructed views of a tall mountain and the surrounding foothills. View corridors were about 100 - 120 degrees throughout the plat - absolutely spectacular! It did cost more for roads in linear feet since I had to run gentle switchbacks up the slope but my investor got more than his fair share of profit out of the end result!
Laying out the homesites to create as spacious a feel as possible can make the difference between average and great profitability. Variances in terrain cause development and construction challenges, but also the opportunity to position homesites for privacy and/or possible views. These days positioning front or rear elevations of a homesite to capture the view of even a small hilltop, or to avoid a direct view of a neighbor can mean thousands in sales price revenue.
Not all land developers clear homesite building envelopes and install rough driveways, but I do. This helps in buyers being able to visualize where to place the home and what they’ll see. It also puts me in more control of where they actually place it and the direction in relation to the others. Although it’s not required in the contract, I would guess that over 90% of the time my cleared homesite and driveway is exactly where the buyers actually put it.
Topography of a given piece offers both challenges and associated opportunities. Consider the things that can’t be changed because of topography, but also consider how to take advantage of the topographic variances to create the best layout, minimize construction costs and provide the best overall competitive product. Old timers always say the “all the good land is gone”. I totally disagree and you can too if you think of the ways to take best advantage of elevations and contours. Good luck!