Grading and Drainage

site, the landscape architect would then match the slope preferences of each program activity (parking lot, building structures, outdoor use areas, etc.) to the slope analysis map created for the site. At least one preliminary site bubble diagram would be created, eventually leading to the preparation of a preliminary site design plan.

It is interesting how compartmentalized the various topics in a landscape architecture curriculum are presented. Design, plant materials, site grading, history and theory, and other topics are offered as separate courses. The integration of the different subjects generally comes about after graduation and during the apprenticeship phase of professional development. This process of integration—making whole—should occur much earlier than it does, and in some curricula this happens. The accomplished landscape architect thinks about and considers all the elements that are part of a landscape design nearly simultaneously. As the seasoned designer develops a design, the physical manifestation of the design, including grading, planting, materials, and details, are simultaneously in mind, whether drawing by hand or working with a computer. Landforms and all the various terrain features that are the underpinnings of a design are visualized, at least in one’s mind, as a design develops and unfolds in schematic and later phases in the design process. The landscape architect is thinking about elevation—not necessarily in terms of specific numbers but the relative elevation differences—when designing an outdoor space, considering the alignment of a walkway or trail, or how a walkway connects to an entry plaza.

Once a design has been resolved, the relative ups and downs of the designed landscape are translated into contours, spot elevations, and sections. The building blocks for achieving competency in designing (solving)5 grading plans for a project begin with being able to read topographic maps, including understanding scale and understanding various frames of survey reference such as datum terms of elevation and grids. After learning how to read a topographic map, one needs to learn the principles of working with contours, spot elevations, and slopes to arrive at grading solutions. The activity of landscape site grading design requires the knowledge and skills that include the following competency areas:

1. Be capable of integrating landscape site grading as one develops a site design plan and recognizing that site grading provides the underpinnings and three-dimensional framework of a landscape design. Thinking about landform and elevation is equally important to thinking about creation of forms, spaces, and the circulation system linking spaces. 2. Be familiar with drafting (drawing representation) conventions and use of architectural and engineering scales. 3. Be able to read topographic maps and be able to identify landform features such as hills, valleys, and steep and not so steep terrain, and drainage patterns. Be able to determine elevations of any point or feature from a topographic map.

4. Be able to visualize three-dimensional landscape from contours from a published topographic map, such as produced by the

U.S. Geological Survey, or one prepared by a professional land surveyor. 5. Be able to create a land surface, path, or hardscape feature such as an entry plaza that has a prescribed or intentional slope. 6. Be able to manipulate (change or modify) contours in order to create desired landforms and sloping surfaces. Also, one must be able to manipulate contours so as to direct the flow of surface water in a desired direction such as away from a building entrance. 7. Be able to assign spot elevations in plan and on sections. 8. Be able to calculate the volume of earth moved within a project site and determine the volume of earth or other soil or rock material that needs to be transported to or off the project site. 9. Be able to prepare (draw) grading plans following graphic conventions so that contractors know what to build. The grading plans must be of sufficient detail so contractors can prepare with confidence a cost estimate for doing the required work as depicted in the drawings and other contract documents. 10. Be knowledgeable and understand the pertinent design standards and legal requirements associated with grading. This knowledge base may include functional design requirement of minimum and maximum slopes for various program elements (recreation fields, parking and circulation, and handicap access––standards for persons with ambulatory and other physical disabilities). 11. Be able to prepare grading plans that meet standards of care related to meeting public health, safety, and welfare design standards. That is, to produce grading plans that limit and reduce the chance of public harm, such as physical injury. 12. Be able to develop grading designs that fall within project budget constraints while meeting the client’s program and functional requirements.

The preparation of site construction plans involves the collaboration of many disciplines. The typical team of consultants might include a landscape architect, a civil engineer, a land surveyor, an architect, a geotechnical engineer, and structural and electrical engineers. Professional land surveyors prepare the site survey and what serves as the base drawing for much of the site grading work required.

A landscape architect, civil engineer, or both in collaboration, typically prepare site-grading plans. How the two collaborate will vary by project. It is common for the landscape architect to prepare a preliminary site-grading plan during the schematic and design development phases of a project. These plans lay the foundation of the landscape grading, including the earth forms, slopes, and critical elevations of hardscape areas and structures. The civil engineer may then take over in the design of storm-water systems, principally sizing catch basins and below ground piping systems determined by runoff and infiltration calculations and the sizing of drainage channels. The civil engineer may also prepare the final site grading design of roads and parking lots. Assignment of responsibilities is established during the