Topography & Site Planning

The gradient of paths, the use of areas, the placement of buildings, the flow of utilities, visual form = In itself topography sometimes determines design.

Influences of topography on the natural systems of a site:

controls flow of surface water- drainage networkscontrols pattern of erosion and sedimentation influences soil formation and vegetative growthinfluence on microclimate

Influences, of topography on basic land use and site planning requirements:

safety - hazardous slopes or cliffs stability - steep slopes accessibility- steep landformsutilitiesspatial pattern - arrangement of usable spacesviews

What to look for in site reconnaissance:

the shape of the land- drainage patterns and landforms (terrain units)slopes- steepness, cover, aspect

Figure by MIT OCW.

Figure by MIT OCW.

landforms (terrain units)

Five basic slope forms: Straight, Convex, Concave, S-shaped, and irregular .

Figure by MIT OCW.

slopes influence many important aspects of land use and site planning, that they are often used as an environmental criteria in regulating development at the community level.

A slope ordinance is often used in evaluating and regulating the environmental suitability of development proposals by planning agencies in towns and counties.

slope problemsdisturbances:

Mechanical cut and fill and the placement of structuresDeforestationDrainage alteration

Disturbances such as landslides cause $1-2 billion in damages and more than 25 fatalities on average each year.

Setting slope classes

The criteria used to set the slope classes are dependent foremost on the problems and questions for which the map will be employed.

One set of criteria would be the maximum and minimum slope limits of the various uses.

Another would be the natural limitations and conditions of the slopes themselves.

With respect to land use activities, we would want to know the optimum slopes for parking lots, house sites, streets, playgrounds, lawns, and so on.

Slope Constraints on Development

Site with slopes averaging less than 1%:Usually result in areas of poor drainage and larger than normal gravity flowsystems. Otherwise, they offer few development constraints.

Sites with slopes averaging 1 -3%:

usually offer the least topographic constraints. Positive drainage can normally be attained without excessive site re-grading. These sites are suitable for a wide range of development types; unfortunately these are often our best farmlands.

Sites with slopes averaging 3 - 5%:These sites impose only slight constraints, except to developments that require large, fairly flat surfaces, e.g. play fields, parking areas, and major structures such as m manufacturing plants and warehouses.

Sites with slopes averaging 5 - 8%:

Impose slight constraints to developments with small structures and minimal site coverage and support systems. Constraints increasewith the size of structures and with the percentage of site covered. These slopes have a formative impact on site organization, as well as on the orientation of buildings and roads.

ADA- Handicap Ramps- maximum 8.3% or 12:1

Sites with slopes averaging more than 8%:generally impose severe constraints to development. These slopesnormally exclude structures with large footprints and severely increasingthe cost of even small structures. On the other hand, unique visual

amenities often make these sites desirable places on which to build.

Topographic Constraints Upon Development

Average Site Large Scale Industrial etc.

Small Scale Industrial etc.

Moderate Density

Housing etc.

Low Density Housing Area

etc.

Organized Play SoccerSlope %

etc. light moderate moderate moderate severe 0-1 s

1-3 none none none none none 3-5 moderate slight slight slight slight 5-8 severe moderate moderate slight moderate 8-15 severe severe high moderate high 15-25 severe severe severe high severe >25 severe severe severe severe severe

For additional informaion about topography, slope, and gradient, pleae visit:

http://www.kaplanaecarchitecture.com/kaplanAECarchitecture/documents/Site%20Planning-Chapter%204.pdf