Planning the Built Environment

Larz Anderson

• Publisher: Routledge
• Year: 2018
• eBook ISBN: 9781351177719
• Topic: Architecture
• Subtopic: Urban Planning & Landscaping

Planning the Built Environment takes a systematic, technical approach to describing how urban infrastructures work. Accompanied by detailed diagrams, illustrations, tables, and reference lists, the book begins with landforms and progresses to essential utilities that manage drainage, wastewater, power, and water supply. A section on streets, highways, and transit systems is highly detailed and practical.

Once firmly grounded in these "macro" systems, Planning the Built Environment examines the physical environments of cities and suburbs, including a discussion of critical elements such as street and subdivision planning, density, and siting of community facilities.

Each chapter includes essential definitions, illustrations and diagrams, and an annotated list of references. This timely book explains new physical planning methods and current thinking on cluster development, new urbanism, and innovative transit planning and development.

Planners, architects, engineers, and anyone who designs or manages the physical components of urban areas will find this book both an authoritative reference and an exhaustive, understandable technical manual of facts and best practices. Instructors in planning and allied fields will appreciate the practical exercises that conclude each chapter: valuable learning tools for students and professionals alike.

Part
I
Land

Chapter
1
Landforms

Definition

Landform—The form, structure, and character of the surface of the land.

Landforms are usually the result of the interactions of various natural physical processes with the surface of the earth.

These processes include stream erosion, wind erosion, glacial action, earthquakes, volcanic action, the freeze-thaw cycle acting on surface materials, the leaching chemicals from rocks and soils, and the deposit of winder water-borne materials. These processes are usually (but not always) very very slow.

Mankind also makes significant impacts on landforms through actions such as draining lakes and marsh areas, flooding lowland areas, massive grading operations, and diverting rivers. Man-made impacts on landform are usually very small in size, but very rapid when compared to the scale and pace of geologic change.

The Importance of the Study of Landforms to Designers of Urban Areas

Landforms are important to designers because they often place substantial limitations on the location, intensity, and character of urban development. For example, in some areas it is difficult or expensive to build because of steep slopes, extensive rock formations, or the presence of water; in other locations, it is dangerous to build because of natural hazards such as flooding, landslides, earthquake hazards or shoreline erosion.

On the other hand, landforms often identify opportunities because they may show locations that are most suitable for urban development, areas suitable for the exploitation of natural resources (through farming, mining, and forestry), or areas where the natural features are of such ecological importance or social value that they should be preserved.

How Landforms Affect Urban Development

Mountains and steep hillsides—Roads and buildings are difficult and expensive to build iii mountainous or steeply sloping hillside areas. Their construction is relatively expensive because of the cost of excavating the uphill section of a road right-of-way (ROW) or a level building site, and the cost of filling and compacting the downhill section. Aside from the economics of development, grading in hillside areas may have very serious adverse environmental impacts: it can cause severe soil erosion and can disrupt much vegetation.

Rocky hillside areas may experience rockfalls, especially in the freeze-thaw cycle of winter-spring. Avalanches may occur in areas with heavy snowfalls. Some soils tend to lose their cohesion when they are saturated with water. If they are on a steep hillside, the force of gravity pulls them downhill which may result in a landslide.

Vee-shaped valleys—The bottoms of these valleys usually have rivers or streams which pose flooding problems, and the steep sides of the valleys may be expensive building sites. Flash flooding is often a serious threat in these valleys.

Flood plains—Many plains are subject to periodic flooding, especially those located where there is no place into which the flood waters can drain. These areas are often suitable for agriculture but may be hazardous for urban development.

Bare rock—These include areas where the depth to bedrock is slight. Installation of underground utilities is difficult and expensive. Grading for level building sites or parking lots is expensive. In some cases, it may be more economical to leave the landform alone and build structures above it.

Sand—Wind blows sand around. You may find that sand intrudes on urban development and may cover it over as the years go by or the sand around and under the development may be blown away.

Lakes—It is possible but often expensive to build urban development on barges or houseboats. Or, piles can be driven down to a firm bearing soil (or to the point of resistance) and used for foundations, but that's expensive, too. Installing underground (or underwater) utility lines is also a severe problem. Of course, there are environmental costs to be considered; they are usually significantly adverse.

Marshes, bogs, and mud flats—These have problems that are similar to those present in lakes, although the water is thicker in them. Some of these areas can be drained and developed, or filled and developed. Note, however, that areas which have water on their surface (seasonally or more frequently) are classified as "wetlands," and most of them are considered to be valuable ecological resources. Current legislation places severe restrictions on how they may be used or modified.

Shoreline areas—Shorelines adjacent to the Pacific Ocean are sometimes inundated by tsunamis ("tidal waves"). On the Atlantic and Gulf coasts, hurricanes occasionally do great damage to shoreline development.

Earthquake areas

• Sites which are crossed by a fault zone— Often, when an earthquake occurs, the land on one side of the fault moves, while the land on the other side of the fault does not. This plays havoc with any building foundations and underground utilities that straddle the fault line.
• Sites which are not directly on, but are in the vicinity of, a fault zone—These areas may experience severe shaking, which may cause substantial damage to aboveground structures in the area. Underground utilities may be compressed and then stretched by the shaking motion, which may cause severe damage or failure.
• Sites which undergo liquefaction—When some soils contain substantial water, they may undergo "liquefaction" when shaken by an earthquake, causing them to act like a liquid for a brief period of time. This can result in slides or slumps of the soil, and destroy the foundations of any structures built on them.

The Influence of Landforms on the Location of Cities

The earliest cities appear to have been built in areas where it was easy to grow crops. This often meant that their locations were on or adjacent to the flood plains of rivers such as the Nile, Tigris, Euphrates, and Indus.

Many of the earliest North American cities were built in coastal areas where there were good harbors. The cities of Boston, New York, and Charleston are examples. Cities (such as Montreal and St. Louis) were also built in inland areas which were accessible by ships and barges using navigable rivers.

Later, as the interior of the country was being settled, canals were built to provide water-borne transportation. The alignment of these canals, of course, had to observe the local landforms. Most often they followed existing river bed...

Table of contents

• Cover
• Half Title
• Title
• Copyright
• Contents
• List of Figures
• List of Tables
• Acknowledgements
• Introduction
• PART I—LAND
• PART II—UTILITIES
• PART III—TRANSPORTATION
• PART IV—RESIDENTIAL AREAS
• Appendix A Exercises (Listed by Chapter)
• Appendix Β Using This Book as a Classroom Text
• Appendix C Derivation of Equations Which Relate Building Height, Density, and Coverage
• Index