Chapter 4 The site.
Upon completion of this chapter, you should be able to
* define the word site and explain its significance in the development of a landscape
* list the typical features that must be evaluated on most sites
* describe sources of site information
* explain geographic information systems
* define the following terms: setback, zoning regulations, property lines, right-of-way, easement, and zero lot line
* describe the limitations that the terrain imposes upon human activities
* understand the basic concepts of land grading
* describe how to prepare a base map
The word site refers to a piece of land that has the potential for development. Sites come in all sizes and shapes and serve a myriad of purposes from residential to commercial, institutional, recreational, and beyond. While there may be a striking similarity between sites, one thing is definite: no two sites are identical. The dissimilarity may be macroscopic or microscopic; it may be cultural, physical, or natural; it may be above ground or below ground. Regardless of what the differences are, they are real. Each site has its own personality that must be identified by a designer or anyone whose work will impact the site. The site is the single most important determinant of what the landscape can and cannot do. It often holds secrets that must be discovered before development can begin. It is the stage upon which the landscape is set, so it must be inventoried, analyzed, plotted, and fully understood if its use is to be totally optimized.
Site Features and Characteristics
The first step in becoming acquainted with a site is to take an inventory of what is there. While the property owners can be an important source of information about the site, it is best for the designer to make the first visit to the site without the owner or client tagging along. It is too easy for the designer to begin seeing the site through the eyes of the owner and thereby assimilating his or her opinions and biases about the site. The designer needs to remain apart from the preconceptions of the site's potential and instead have an organized method to assess the many and varied nuances of each site.
Separating the features and characteristics of a site into categories is a logical place to begin. Some of the site's characteristics are natural features, while others are man-made. Still others are cultural (resulting from or associated with human society). Some features are totally physical, while others are most significant as visual features. Some features are unmistakably positive factors, and others are definitely negative in their impact. Many have a neutral quality until they are judged in the context of the proposed design.
A partial list of the features and characteristics that are inventoried and later evaluated during the site analysis includes the following.
a. terrain (rise and fall of the land)
b. topography (the record of an area's terrain)
c. slopes (their steepness as measured at different locales within the site)
d. erosion (both present and potential areas on the site)
e. directions of surface water drainage
f. areas of puddling or drought
g. soil qualities (pH, nutrient level, stoniness, depth of the topsoil, texture)
h. existing plant materials (quantity, quality, species names, sizes, locations)
i. microclimates (protected or exposed area, where plant growth may be affected)
j. prevailing winds
k. annual rainfall and snowfall on the site
l. depth of the frost line
m. off-site views
a. existing buildings (size, architectural style, color, materials)
b. utilities (above and below ground)
c. paved areas, such as drives, existing patios, basketball or tennis courts
d. existing landscape features, such as walls, pergolas, fences, pools
e. building details, such as the location of doors, windows, utility meters, air conditioners, downspouts, dryer vents, exterior mounted lights
f. current storage spaces for trash containers, garden tools, recreational vehicles
g. adjacent property development Cultural Features
a. property lines (legal lines that define the parameters of a lot)
b. setback (the minimum distance that structures, including walls, fences, pools, and outbuildings, can be located from a property line)
c. zoning regulations (legal restrictions on specified uses of land in an area)
d. deed restrictions (limitations on the use of certain materials in an area, or the requirement for a certain material or quality standard, usually imposed by an association of local owners)
e. right-of-ways (municipally owned strips of land that are usually between the road and the front property line of a private property--there are usually restrictions on what the property owner can place within the right-of-way)
f. easements (strips of land within the site that are legally accessible by utility companies--property owners are usually restricted in what they are able to place within an easement in case the utility companies want to use it to place or access their lines)
g. zero lot lines (the absence of any side-yard setback requirements on adjacent sites, thereby permitting two buildings to be built right next to each other--such absence is common to multiple housing developments)
h. off-site noises or odors
i. historical significance of the site or nearby area
Sources of Site Information
As the above list illustrates, the features of a site are varied. Some are easy to measure and evaluate, but others are more complex and may even be beyond the capability of the designer or landscape firm's staff to assess without assistance. It is not uncommon for the input for a site inventory to come from multiple sources. Typically, things that require onsite counting or measuring or sample collecting can be done by the landscape company. Features that require expertise not common to the company may be described and recorded by other professionals, and that information may then be used by the designer. For example, the topography of a site can be read from a topographic map that has been charted and recorded nationally by the U.S. Geological Survey (USGS), Figure 4-1. The USGS maps are produced in several scales (1 inch = 2000 feet, 1 inch = 24,000 feet, and smaller). They are most useful for describing the terrain of large areas and they benefit designers working with large, nonresidential sites. Other sources of topographic maps may be local state, county, or city administrative offices. For smaller sites, the government maps are often not as helpful as a topographic survey map prepared specifically for the site by a licensed land surveyor. The surveyor may work within the landscape company or may be hired just for that job. These maps are drawn to a larger scale and provide much more usable information about the site. On other projects, a surveyed record of the entire site may be unnecessary, but the designer may need to know the steepness of a single slope in order to develop the plans for a retaining wall or a set of steps. On another site, existing grades may need to be modified in order to allow the development of a drive or a patio, or existing buildings may need to be measured and located on the base map. In such situations, it is important that the designer know how to measure the key features on the site and take simple surveys of the land.
Soil factors may also be evaluated using data obtained by the landscape company entirely or with the aid of other agencies and services. On a residential site, the most important informational needs may be soil pH, texture, drainage, and depth of the topsoil. That information can be gathered easily by the company. If soil nutrition is a concern, the landscaper may take a soil sample and test it herself or send it to a private laboratory for analysis. On large-scale projects, more in-depth information may be needed. Some of that data may be obtained from soil survey maps available from the U.S. Department of Agriculture's Natural Resources Conservation Service. These maps can provide information like the depth of the bedrock on a site, the location of the water table, the permeability of the soil to water, and the general soil type(s) on and near the site.
Weather data cannot be gleaned from a visit to the site. If the landscaper does not have a long-term familiarity with the area and its year-round weather, it can be helpful to consult the local weather records. Those records can provide information about the average annual rainfall, snowfall, and days of sunshine. Also available will be information about predictable temperature ranges, average humidity, and wind records.
Locating the actual property lines of a site can be difficult at times. Often what appears to be the property line, or even what the owner believes is the property line, is not. Hedgerows, fieldstone walls, fences, pavement edges, and similar landmarks that separate properties may be the accepted separation between lots but not be the legal separation. The county clerk's office is usually the place of filing for property records. The legal boundaries of a site can be found there.
Other cultural characteristics of a site can be legal, architectural, historic, or the simple trappings of our civilization. How the land was used in earlier years may have a bearing on how it can be used in the present. Was it a landfill? a cemetery? a disposal site for chemicals? a battlefield? Are there tax advantages or other incentives for using the site for certain purposes? Are the buildings or other structural features on the site illustrative of a distinctive style of architecture or period of time, such as the Victorian era or the Art Deco period? Are there underground wires or pipes or telephone lines? Are there nearby sounds that are welcome or offensive, such as church bells, factory whistles, or heavy traffic? The same concerns can apply to smells. It could be a bakery or a slaughterhouse, but the impact of periodic aromas would be part of the character of a site being inventoried. Many of the cultural features of a site can be ascertained by a designer simply visiting the site. Other features may need to be researched. Local historic societies, owners' cooperatives, local architects, utility companies, longtime neighborhood residents, and various municipal agencies can provide useful information about the site.
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Geographic Information Systems
In recent years, the analysis of the suitability of certain sites for large-scale development has been aided by a powerful technology known as geographic information systems. These systems have gained widespread acceptance and use by landscape architects during the past two decades. While the data provided by the systems can be applied to the analysis of small sites, their most frequent use is with larger nonresidential projects.
Geographic information systems are computerized systems that combine both hardware and software to provide mapping data about geographic regions of the country. Unlike aerial photography that merely locates the physical features of a site, geographic information systems provide data on a site's topography and physical resources, wetlands, aquifers, surface water features, physical infrastructure, administrative boundaries, historic landmarks, and regulated areas such as airports, government properties, and underground storage areas. Landscape architects have embraced the technology of the systems because they can access an immense amount of data in a short time and gain a faster understanding of the site than through any other means. Again, it is a technology that is not commonly used in residential design, but it has a broad spectrum of use in most other areas of design and development because it offers rapid and documented evidence of a site's suitability or lack of suitability for various uses.
Reading the Terrain
As noted previously, the rise and fall of the land describes its terrain and is recorded as its topography. Topographic maps, whether prepared by the USGS or a private surveyor, will represent vertical changes in the terrain as broken lines termed contour lines. The lines represent a vertical rise or fall over the horizontal distance measured from the map's scale. Each contour line connects all of the points of equal elevation on that map, and each is labeled to indicate its elevation. The vertical distance between contour lines, the contour interval, is always stated on the map. Steep slopes are identified by closely spaced contour lines. Gradual slopes are denoted by more widely spaced contour lines. See Figure 4-2.
For large sites, the USGS maps may provide satisfactory data for a designer to use in a landscape. The maps are available for most areas of the United States and may be purchased at a nominal cost from regional offices of the Survey. For smaller sites, the scale of the map may need to be smaller and the contour interval as precise as 1 foot between the lines. Those types of topographic maps typically require preparation by a professional surveyor.
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Figure 4-3 illustrates some of the land forms recognizable from a topographic map. In order to interpret the map fully, students should know the following points regarding contours and contour lines.
* Existing contours are always shown as broken lines.
* Proposed contours are always shown as solid lines.
* Contours are labeled either on the high side of the contour or in the middle of the line.
* Spot elevations are used to mark important points.
* Contour lines neither split nor overlap (except in overhangs).
* Contour lines always close on themselves. The site map may not be large enough to show the closing, but it does occur on the land.
* Runoff water always flows downhill along a route that is perpendicular to the contour lines.
Once the contours of a site are known and plotted, slopes can be measured and analyzed. Slopes are measurements that compare the horizontal length (measured from the map's scale) to vertical rise or fall (as determined by the contour lines and contour interval). Slopes may be expressed as ratios or gradients and percents. As a ratio or gradient, the horizontal space required for each foot of vertical change in elevation is compared as V:H = R where V is the vertical distance, H is the horizontal distance, and R is the ratio or gradient. Ratios are commonly expressed as 1:3, 1:4 and so forth, Figure 4-4. As a percent, the vertical distance is divided by the horizontal distance and the answer is expressed as 33 percent, 25 percent, and so forth. Another way to visualize the percent of slope is to picture the slope extending along a horizontal distance of 100 feet. The vertical distance then becomes comparable to the percent of slope, Figure 4-5.
The Need for Terrain Information
The ease or difficulty of development depends upon whether the land is level or rolling, rocky or sandy, forested or open. A study of the terrain also supplies answers to basic questions: Where does the surface water flow? Will water collect in puddles anywhere? What types of human activities can take place? Will grass grow on that slope? Can a car be parked safely on that slope?
Most human activities require that the land be level or nearly level. Land that is 5 percent or less in slope is perceived by users as flat. Flat land is the easiest terrain to develop, but it may be difficult to move off surface water. A slope of at least 1 percent is usually necessary to drain away surface water on turf and other planted landscape surfaces.
Human activities can usually take place on a slope of 5 percent to 10 percent, but users will sense the uneven footing. Land that slopes more than 10 percent may require alteration (grading) to make it more usable. Figure 4-6 lists acceptable slopes for various landscape components.
Grading the Land
When the land is not suitable for the activities planned for the site, it may be necessary to reshape it. The form of the land is changed by a process called grading. Grading can be as simple as one worker leveling and smoothing a small area of earth with a spade and a rake and hauling away the leftover soil in a cart. It also can be so extensive that massive bulldozers and dump trucks are required to chew up and haul away entire mountains. Regardless of the extent of the project, grading is usually done for one of four reasons:
* To create level spaces for the construction of buildings
* To create the level spaces required for activities and facilities such as parking lots, driveways, swimming pools, and playing fields
* To introduce special effects or improved conditions into the landscape, such as better drainage, earth berms, tree wells, and ponds
* To improve the rate and pattern of circulation by means of better roads, ramps, tracks, or paths, Figure 4-7
[FIGURE 4-3 OMITTED]
When earth is removed from a slope, the grading practice is called cutting. When earth is added to a slope, the practice is called filling. On a contour map, a cut is shown as (1) a solid line diverting from and then returning to an existing contour line, and (2) moving in the direction of a higher contour. A fill is shown as (1) a solid line diverting from and then returning to an existing contour line, but (2) moving in the direction of a lower contour line. See Figure 4-8. A typical graded slope is illustrated in Figure 4-9.
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Because the grading process can involve the movement of tons of soil and rocks, designers should approach such specifications cautiously. In cut and fill operations, the soil that is removed from the cut should be used to create the fill whenever possible. This practice minimizes the need for costly hauling and disposal. If possible, the topsoil layer should be stripped away and stockpiled before grading begins. The topsoil can then be spread over the finished grade before the site is replanted.
When land is graded, not only is the topsoil disturbed, but the surface water drainage and vegetation are disturbed as well. Water must drain away from the buildings, not toward them. Freshly graded slopes must be stabilized to guard against erosion. The surface roots of valuable trees must be protected from the destruction of cutting and the suffocation of filling. Figure 4-10 shows a typical slope before and after grading. Figures 4-11 and 4-12 show common techniques for dealing with trees that exist before the grading of a site.
Preparing a Base Map
A base map is a graphic depiction of the site features that were collected, measured, and inventoried as described previously. It enables the designer to take a look at the big picture after the individual snapshots of the site are pieced together. It is a plan view drawing that locates the existing buildings, their windows, doors, and other significant features; the existing hardscape such as drives, parking areas, walls, patios, etc.; all existing plant materials; and other physical items noted during the site inventory. The base map can also plot out the location of the setbacks, the easements, the underground utility lines, and overhead wires. It is also an opportunity to make notations about the direction of prevailing winds, surface water patterns, and attractive or offensive off-site features that impact the site. Only after this physical arrangement of the inventoried site features is prepared can the designer begin the next stage of the design process: the analysis of the site and the determination of how suitable or unsuitable it is to accommodate the client's program requests.
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Most designers will follow the preparation of the base map with a drawing developed as an overlay that eliminates all of the existing features that they plan to eliminate from the new landscape. The terminology for the revised drawing is not uniform. Some designers continue to refer to it as the base map, while others give it a new name, the base sheet. Regardless, both versions are of great value to the designer and must be carefully prepared and drawn to scale. Neither is likely to be seen by the clients.
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Throughout the site data inventorying process, it will be helpful if the designer takes photographs of the site. These photos will have varied and repeated uses throughout the design process, not the least among them being the benefits they will afford as the base map and the later overlay are prepared.
A. Indicate if the site characteristics listed are (N) natural, (M) man-made, or (C) cultural.
1. condition of the turf
2. nearness of public transportation
3. rock outcroppings
4. swimming pool
5. terrain features
6. off-site views
7. buildings on the site
8. style of the architecture
9. existing shade
10. prevailing breezes
11. soil conditions
12. historical features
13. provisions for parking
14. nearness of neighbors
15. presence of wildlife
16. traffic sounds
17. zoning regulations
18. presence of large, old trees
19. existing lighting
20. surface water patterns
B. Define the following terms.
3. contour line
4. contour interval
6. property line
8. zero lot line
10. zoning regulations
C. Complete the following sentences that describe the characteristics of contours and contour lines.
1. Existing contours are always shown as
-- lines on topographic maps.
2. Proposed contours are always shown as
-- lines on topographic maps.
3. Contours are always labeled on the
-- side of the contour or in the
-- of the line.
4. Important points on topographic maps are marked by --
5. A 1:3 or 1:4 comparison is the -- of a slope.
D. Label the parts of a typical cut and fill in the diagram below.
E. Identify the land forms A through E on the contour map on the following page.
F. List five examples of landscape projects that might benefit from the data obtainable through the use of geographic information systems.
1. Fill several greenhouse flats with loamy soil. Plant several with a local turf grass. Obtain another flat (perhaps from a local nursery) that is filled solidly with English Ivy, Periwinkle, or similar vining groundcover. Plant or obtain another that has an established growth of a typical roadside embankment stabilizer, such as crown vetch. Tip the flats to create various slopes up to 50 percent. Water all flats with the same amount of water applied from a sprinkling can to simulate rainfall. Record the erosion noted over the weeks at each degree of slope. Record also the quality of the turf grass growth at increasingly steeper angles.
2. Build a small contour model from the information on a topographic map. Use cardboard of a thickness comparable to the contour interval on the map.
3. Order topographic maps of the local area from the U.S. Geological Survey. Find recognizable local features on the map to help students visualize how the contour lines describe terrain variations.
4. Obtain soil survey maps of the local area and let students match the soil types described on the maps with actual samples that they take.
5. Invite a land surveyor to visit the class to demonstrate the use of surveying instruments and explain how land surveys are done.
6. Have students take measurements of a nearby property and then prepare a base map of the site.
Jack E. Ingels
State University of New York
College of Agriculture and Technology
Cobleskill, New York
Figure 4-6 Recommended slopes for common landscape components PERCENT OF SLOPE LANDSCAPE ILLUSTRATED COMPONENT ALLOWABLE IDEAL EXAMPLE SITTING 1/2% TO 3% 1/2% TO 2% ILLUSTRATED AREA, PATIOS, EXAMPLE TERRACES 2% AND DECKS LAWNS 1% TO 5% 2% TO 3% [ILLUSTRATION OMITTED] 3% WALKS 1/2% TO 8% 1% TO 4% [ILLUSTRATION OMITTED] 4% DRIVEWAYS UP TO 11% 1% TO 11% [ILLUSTRATION AND OMITTED] RAMPS 10% BANKS UP TO 33% 16% TO 33% [ILLUSTRATION PLANTED OMITTED] WITH 30% GRASS BANKS UP TO 50% 20% TO 33% [ILLUSTRATION PLANTED OMITTED] WITH 33% GROUND- COVERS AND SHRUBS STEPS UP TO 65% 33% TO 50% [ILLUSTRATION OMITTED] 50%
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|Title Annotation:||SECTION 1 Landscape Designing|
|Author:||Ingels, Jack E.|
|Publication:||Landscaping Principles and Practices, 6th ed.|
|Date:||Jan 1, 2004|
|Previous Article:||Chapter 3 Graphic materials and techniques.|
|Next Article:||Chapter 5 The landscape process.|