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.

Planner Speak: What on earth is a streetscape?

You have probably brought back photos of stunning landscapes from a vacation, but what about a streetscape? If someone asked you to take a picture of a streetscape, where on earth would you point your camera?

Streetscape (n.) is the appearance of the street, including the entire area between the buildings on either side of a street. Elements of the streetscape include:

  • the front sides of the buildings;
  • landscaping, such as trees, grass, flowers, and bushes;
  • stormwater management features;
  • sidewalks;
  • signs;
  • street furniture, such as benches, bike racks, trash cans, and water fountains;
  • street lights;
  • features of the road including crosswalks, bike lanes, cycle tracks, parking spaces, travel lanes for cars, dedicated lanes for buses, and medians; and
  • street paving, such as asphalt, concrete, brick, or stone.

17th Street     Flick-user-la-citta-vita-CC-BY-SA-2

Paul-Krueger-CC-BY-2.0-v2     Baker-Co-Tourism-CC-BY-ND-2.0

The streetscape can make a big difference as to whether or not people enjoy and feel comfortable traveling down a street, regardless of if they are walking, biking, driving, or riding transit. Trees and awnings can provide shade or shelter from the rain for people who are walking.  A wide sidewalk, without obstacles in your path, makes it easier to walk side by side and chat with a friend, push a stroller, or get around in a wheelchair. A row of landscaping between cars and a bike lane, also known as a protected bike lane, can make it more comfortable to bicycle on a street with lots of traffic. Walking next to buildings with lots of windows with interesting things to look at is more enjoyable than walking next to a solid, blank wall or a large parking lot that separates the buildings from the sidewalk. Lighting that is directed towards the sidewalk can make it feel safer to walk at night.

The streetscape can also make a big difference as to whether or not a street is a comfortable and attractive place to stop and stay for awhile. Outdoor seating in front of a restaurant allows people to enjoy a meal and watch people passing by. Covered bus shelters can protect you from the elements while you wait for the bus. Bike racks in front of stores give you a place to lock up your bike so you can feel confident that it will be there when you return from running your errands.

If you’d like to try your hand at designing a streetscape, check out Streetmix. We’d love to see what you come up with! Share your designs with us on twitter by tagging @RPAchat or on facebook by tagging @chcrpa.

Planner Speak: What is a flood plain exactly?

When the roads get wet and slippery I know that my car can hydroplane. Can it flood plain too? What is a flood plain exactly?

A flood plain (n.) is the area next to a stream or river that may be covered with water during a flood.

The Federal Emergency Management Agency (FEMA) maps flood plains based on the risk and type of flooding. One line that FEMA draws is the boundary of the 100-year flood zone. Every year there is a 1% chance that flood waters could reach or pass the boundary line of the 100-year flood zone. Don’t let the name mislead you. It is possible for a lot of the land within the 100-year flood zone to flood on a fairly regular basis, far more often than once every hundred years. FEMA considers these lands to be Special Flood Hazard Areas, with a high risk of flooding.

FEMA also maps the boundary line of the 500-year flood zone. Similarly, every year there is a .2% chance that flood waters could reach or pass this boundary line. FEMA considers these lands to have a moderate risk of flooding.


The interactive map below shows the 100-year and 500-year flood zones in Hamilton County as well as the floodways. The floodway is the channel of a river or stream as well as the land next to the channel that has to stay open to carry the deeper, faster moving water during a flood. In the map below, the floodway is blue, the 100-year flood zone is red, and the 500-year flood zone is pink.

Flood plains protect the health and quality of our rivers, lakes, and streams and the water that comes through our faucets. They help to control the flow of water and can absorb pollutants and sediments, such as gravel and clay, before they drain into streams and rivers. Flood plains are home to many types of plants and wildlife, including threatened and endangered species. It is important for communities to protect our flood plains both to keep our rivers, lakes, and streams healthy and to keep our homes and businesses from being damaged by floods.

Planner Speak: What do you mean by zoning?

You’ve probably gotten “in the zone” while doing something you enjoy, be that baking a cake, playing an instrument or going for a long run, but what do planners mean when they talk about zoning?

Zoning (n.) categorizes properties in a city or county into different classifications called zones.  Each zone has a set of rules about features of development such as the land use, height of buildings, amount of parking, and density. In the past, zoning has been more concerned with the land uses allowed in each zone than the form of development. As a result, common zoning categories are often residential, commercial, office, manufacturing, warehousing, and agricultural.

You might have heard about zoning in the news when a property owner needed a change of zoning for a development project. To learn more about the rezoning process, check out the Development Services page on the RPA website.

Why do we use zoning? Originally, zoning was created to prevent conflicts between different types of land uses. For example, zoning can be used to keep a large factory, which might produce loud noises and odors, from being built right next to homes.

A zoning ordinance has two major parts: text and a map, or several maps. The text explains the rules for each zone. The map applies the zones to sections of land. Unincorporated Hamilton County and each town and city in the county have their own zoning ordinance. Here are links to the text sections of the zoning ordinances. Here is a zoning map for Hamilton County. Do you know what the zoning is for the property you live on? To find out, click the house icon in the toolbar in the top center of the screen and type in your address. Then, click on the RPA icon to the right of that and click on your property.


Below is a map of the zoning in the MLK Neighborhood of Chattanooga. Properties are color coded according to their zone, and the letters followed by numbers are abbreviations for different zones. For example, the light yellow properties are in the R-1 Residential Zone, the red properties are in the C-3 Central Business Zone, and the bright purple properties are in the M-2 Light Industrial Zone.


Traditional zoning, or zoning that is more concerned with the land uses allowed in each zone than the form of development, is the type of zoning that we see in Hamilton County and the towns and cities in the county. Traditional zoning usually does a good job of preventing conflicts between land uses. However, because it separates land uses, it often means that jobs, shops, and homes are separated from each other. The distances between different types of land uses mean that most people in our county have to drive to get to the places they want to go on a daily basis.

Through our ‘What do you want to grow?‘ game, we learned that two of the public’s top priorities are “neighborhoods with jobs, shops, and grocers” and “transportation options”. Many cities are turning to more innovative types of zoning, such as form-based codes, for neighborhoods that want to have jobs, shops, and homes close together, where it is possible to walk, bike, or take transit to get to the places you go on a daily basis. Form-based codes focus more on how buildings are designed and how they fit in with their surroundings than on the land use. Form-based codes still have rules about land use, but there is more focus on how buildings fit in with the network of streets, public spaces, and other buildings around them.

In the ‘Growing Forward’ planning framework, we will update our codes and policies in step three, ‘Building the Future’. Creating form-based codes for certain districts and neighborhoods may be a part of the code update. In fact, last Tuesday the Chattanooga City Council discussed a demonstration project that would create form-based codes for five different areas in Chattanooga. One of the reasons for updating our codes is to make sure they help us fulfill the vision that we set in step one, ‘Renewing Our Vision’ and step two, ‘Strategy For Great Places’. Now is the time to get involved to help us build a stronger and more vital place to live, work, and play. Keep an eye on our event calendar for upcoming meetings. At these meetings, you will have the chance to review and make suggestions about our goals, the very goals that we will use to guide changes to our codes and policies.

Planner Speak: What exactly is economic development?

You’ve probably heard about decisions that were made, policies that were adopted, money that was spent, of land that was purchased in hopes of spurring economic development, but what exactly is economic development?

Economic development (n.) is actions that communities take to improve the economy and people’s well-being. Economic development can involve:

  • supporting existing businesses;
  • helping new businesses get started;
  • training or recruiting people for jobs;
  • making sure spaces are available for new businesses; and
  • making sure infrastructure that businesses need is in place.


PopUp          ChattState


One part of Chattanooga’s infrastructure that community leaders hope will support new businesses and jobs is gigabit-per-second internet. Chattanooga Mayor Andy Berke has put forward the idea of creating an “innovation district” to build upon the fast, cheap internet service. The district would bring companies that develop technology and conduct research to a central location where they can work together and have easy access to housing and services like restaurants.

Why do communities get involved with economic development? Some of the goals include keeping jobs in the area, bringing more jobs to the area, bringing in more tax money, keeping the economy stable, increasing the amount of products and services the community is able to produce for itself and sell to other areas,  keeping money in the community, and reducing poverty. 

Who is responsible for economic development? Quite often governments, non-profit organizations, and private companies work together on economic development projects. The redevelopment of Downtown Chattanooga and the riverfront is a good example of public-private partnership. The government, non-profits, and private companies worked together to plan, pay for, and build the development that we see today, including the Tennessee Riverpark, the Tennesse Aquarium, and the many hotels and businesses.


To learn more about some of the agencies and organizations that are working on economic development for our area, check out the links below:

Planner Speak: So what do you mean by affordable housing?

If I can pay my rent or mortgage, then my home is affordable, right? What does it mean to have affordable housing, and how do I know if I’m paying the “right” amount for my housing? 

Affordable housing (n.) is a place to live where you can spend 45 percent of your household income or less on your housing and transportation. Household income is the money that people who live together in a home receive.


In the past, when planners looked at housing in a community to see if it was affordable, they did not consider the cost of getting around. Planners used to think that housing was affordable if people could spend 30 percent of their income or less on their housing. Now, planners have started to realize that transportation costs affect whether or not a home is affordable. For example, you may spend less than 30 percent of your income on your housing, but if your home is two hours from your work, and you have no choice but to drive by yourself to get to work, you might spend more than 45 percent of your income on your housing and transportation costs. That means you will have less money for other things like food, clothing, and medical care.

The location of a home and the multimodal transportation options available in the area affect whether or not the home is affordable. If your job and shops are near your home, you won’t have to travel as far to reach the things you need on a daily basis. If it is easy and convenient for you to walk, bike, ride a bus or a train, or carpool, you won’t have to spend as much money as you would if you had to drive by yourself. Having the things you need close to your home and having cheaper ways of getting around mean that you can spend less money on transportation.

Below are two maps showing affordable housing in Hamilton County and the surrounding area based on two different definitions. In the map on the left, the areas in yellow are considered affordable if you only look at housing costs. In the yellow areas, people typically spend less than 30 percent of their income on housing.  In the blue areas, people typically spend more than 30 percent of their income on housing.

In the map on the right, the areas in yellow also represent affordable housing, but this map also looks at transportation costs. In the yellow areas, people typically spend less than 45 percent of their income on housing and transportation. In the blue areas, people typically spend more than 45 percent of their income on housing and transportation. As you can see, far fewer areas in Hamilton County are affordable when you include the cost of both housing and transportation. You can check out the map to see how our area compares to other areas or click the arrow to the right of the legend to look at more detailed information.

H+T index

In 2013, the Regional Planning Agency completed a Housing Study for Chattanooga. You can read more about affordable housing on page 35 – 40 of the study and strategies for making housing more affordable on page 46.  

Now that you know what we mean by affordable housing, tell us, is your housing affordable?

Planner Speak: What on earth is infill?

It isnt’ an abbreviation for infiltrate. It isn’t what you’re supposed to do when you see “Name:                   ” written on a form.

Infill (n.) is the development of vacant or underused land in an area that already has roads, sewers, electricity and even possibly existing buildings1. An infill project could range in size from a small addition to an existing building, to the redevelopment of a single lot or an entire block.

Taking a vacant lot or an empty building and turning it into a place where people can live, do business, or do both, can bring new life and energy to an area. It also increases the tax base for the area. Developing in areas that are already built-up helps to preserve open space, farm land, and forests. It also makes use of the infrastructure that is already in place, which reduces the cost of providing new roads, sewer lines, fire stations and other facilities and services for the development.

WA-infill      NC-infill

When planners and developers work on an infill project, it is important for them to determine if the infrastructure can support the additional people that the development will bring to the area. For a new housing development, for example, the planners and developers should make sure that the roads can carry the additional traffic and the schools have room for the children that might live in the new homes.

It is also important for developers and planners to involve the community early in the development process. That way neighbors can provide input about the design and ask questions about how the development will impact the community. Developers and planners will be able to determine whether or not the development is appropriate for the community and make sure that any new development fits in with the character of the area.


The vacant lot at 728 Market Street in Downtown Chattanooga is a good example of a potential site for infill development. Here, you can see the redevelopment plan that was created for the site as part of River City Company‘s Urban Design Challenge. To make good use of the site until it can be redeveloped, River City Company transformed the lot into Center Park. Now the park is a place where people can meet up for lunch at the Food Truck Court or relax on the lawn for an outdoor movie screening. You can keep up with events and news of future development on the Center Park facebook page.

1  American Planning Association. (2006). Planning and urban design standards. Hoboken, N.J: John Wiley & Sons.

Planner Speak: What exactly is open space?

What do you think of when you hear the phrase open space? Is it that parking spot that you were so happy to find right in front of the shoe store? Is it the extra storage area you reclaimed in the attic when your grown son finally took his boxes of comic books and actions figures to his own house? Perhaps you think of the space between Earth and other planets, or maybe the chorus of “Wide Open Spaces” starts playing in your head. The Dixie Chicks song probably comes closest to describing what planners mean when they talk about open space.

Open space (n.) is land that is undeveloped or only lightly developed. Meadows, woods, and wetlands, such as marshes and swamps, with no buildings on them are examples of undeveloped open spaces. A dog park, community garden, playground, soccer field, and  walking path through a natural or landscaped area could also be considered open spaces even though people have changed these areas and built small structures on them. These are all lightly developed open spaces.

marsh          subdivision

Land that was once developed but is now vacant can be converted into open space. A good example is the Main Terrain Art Park, which is located on Chattanooga’s Southside at the end point of long abandoned rail lines. Not only does the park encourage physical activity through exercise stations, a running track, and interactive sculptures, but it is also designed to filter and reuse stormwater. 


Open space can be used for recreation or conserved for its benefits to the natural environment. Many open spaces, such as Main Terrain, serve both purposes. Open spaces can benefit the environment by improving air and water quality, providing habitat for wildlife, managing stormwater, and reducing flooding.

The Trust for Public Land is a non-profit organization that works to create and protect open space. Local projects that they have been involved with include the University Greenway, North and South Chickamauga Creek Greenways, Stringer’s Ridge, and the Cumberland Trail. If you love open spaces, you can share why nature matters to you at

Planner Speak: What do you mean by density?

Your elementary school science teacher probably taught you about density. She might have shown you that an orange floats in water, but then peeled it, put it back in the water, and demonstrated how it sinks. She then explained that an orange rind is full of tiny air pockets that help to lower the density of an orange and allow it to float. “Density,” she explained, “is the mass of an object relative to its volume.” When planners talk about density in terms of land use, they have another definition altogether.

Density (n.) is the number of dwelling units per unit of area, such as 30 dwelling units per acre. A dwelling unit is the living quarters for a household, or one or more people who live together.  An apartment, house, townhome, and one side of a duplex are all examples of a dwelling unit. Calculating the density of an area is simple. Just divide the number of housing units by the number of acres.

Housing developments that have the same density can look very different as you can see in the images below. As Julie Campoli explained in her book Visualizing Denisty, “It is not density that makes a neighborhood appealing or appalling, but form – the street layout, arrangement of buildings, quality of architecture, and use of open space.” These are the factors that make a neighborhood feel crowded or spacious. Julie explains that people often assume dense neighborhoods have too many people, may not offer enough privacy, and the homes may be too close together; however, “how we perceive density has everything to do with how it is designed, not the actual ratio of units to acres.” To test your preconceptions of density, you can take this short quiz.

Last year Julie gave a City Share presentation in Chattanooga called Rethinking DensityYou can also learn more about density by visiting the Lincoln Institute of Land Policy site.


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Images Courtesy of the Commonwealth of Massachusetts

Planner Speak: So what is multimodal transportation?

Multimodal transportation may sound like something that only happens in a galaxy far far away, but it is probably something that you do on a daily basis. If you’ve ridden your bike to the bus stop, taken a taxi to the airport, or walked from the parking lot to your office, you are familiar with multimodal transportation.

Multimodal transportation (n.) is the many ways that people and things get from place to place using several different modes of transportation. Walking, biking, wheelchairs, buses, trains, cars, trucks, taxis, airplanes, and boats are all modes, or forms, of transportation.

Planners are interested in making it easy and convenient for people and things to get to the places they want or need to go. To make it easy to get around, planners must consider how to make connections between different modes of transportation.  If the different modes are connected, goods that have traveled from one state to another on a barge can get to their final destination in a truck or people can take a short walk from their offices to get to a shuttle that will take them to their favorite place for lunch.

walking  LJ Bike on Bus  barge

To improve connections between transportation modes, the RPA is working with CARTA, Chattanooga’s Transportation Department, and the Benwood Foundation on a Multimodal Transportation Center Study. The study is evaluating possible locations where car and bike parking, car sharing, bike share,  taxis, buses, and possible future rail service could all come together in one or more transportation centers.

While RPA makes plans to increase transportation options, we also have a Green Trips program that encourages people to take advantage of the wide range of options that are already available in our community. You can learn about different ways of getting around and the benefits of doing so  as well as winning rewards for logging your green trips.