Planner Speak: What exactly is a slope?

If you’re an avid skier or snowboarder, you’re probably looking forward to winter when you can hit the slopes and make fresh tracks through the powder. If a planner told you there are steep slopes in Hamilton County, you might look at him in disbelief. We may have gotten a lot of snow last year, but not enough that someone would consider building a ski resort. What exactly do planners mean when they talk about slopes?

Slope (n.) is the steepness of an area of land, or how quickly the land goes up over a certain distance. You can measure the slope of land the same way you measure the slope of a line in algebra class: by dividing the “rise” by the “run”.


Let’s say that you have a piece of land that is 100 feet long, and it rises 20 feet in elevation from one side to the other. The “rise” is 20 feet and the “run” is 100 feet. If you divided 20 by 100, then .2 would be the slope. Usually, planners talk about slope as a percentage. To covert .2 to a percentage, you would multiply by 100 giving you a slope of  20%.


Typically, a slope of 15 – 25% is considered steep, and a slope over 25% is considered very steep. In Hamilton County, over 30% of our land area has a slope of 15% or greater as you can see in the map below.


Our mountains, ridges, and slopes are key features of our natural, scenic beauty. They can offer a beautiful backdrop, especially when the leaves change color in the fall, or a magnificent view of the valley below. The hilly land is one of the defining characteristics of our local identity. It also makes many of the activities that both residents and tourists enjoy possible including hiking, trail running, hang gliding, mountain biking, and rock climbing.

Signal Mountain

Not only do slopes bring scenic beauty and recreational opportunities to our area, but they also play an important role in the health of our natural environment. Slopes that have not been disturbed provide a home for wildlife and improve water quality by slowing or reducing rainwater runoff. Disturbing a slope could involve removing plants or soil or building something on the slope. Disturbing slopes increases the risk of slope failure or instability, meaning that rocks and soil could start to erode, slide, or collapse. For these reasons, it is important to protect steep slopes: for their scenic beauty, for their recreation opportunities, for their role in the health of the natural environment, and to avoid costly repairs to buildings and the infrastructure, such as roads, that would be needed to provide services to buildings on steep slopes.


  1. Allen miller says

    Steep land is continuously for sale along Fairview Rd. within the city of Chattanooga. This west slope of Big Ridge has been targeted by RPA for decades yet not a single parcel has been acquired for preservation or conservation. The market value can’t be much. Why no action? Poorly conceived developments crop up often and chip away the slope to the detriment of N. Chickamauga Creek and quality of life.
    Allen Miller

    • Cortney Mild says

      Allen, thank you for your comments. The Planning Agency isn’t able to acquire land. The agency has attempted in past plans, and continues to do so in current planning efforts, to draw attention to these lands by defining the areas as ‘steep’ and ‘very steep’ based on the percent slope. However, to staff’s knowledge, only the Town of Walden in Hamilton County has an ordinance limiting development in these defined areas. We are currently updating our comprehensive plan, called ‘Renewing Our Vision’. In our first round of public engagement, the top priority issue for regulatory action was preserving the natural environment. Also, in our recent public workshops, 81% of participants felt that we should discourage development on steep or very steep slopes to some extent. If you were not able to attend the workshops, we encourage you to share your feedback through our Virtual Workshop at You will find a specific question about development on slopes in Activity 2 at

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