Land-Use Planning and Engineering Geology

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Land-Use Planning and Engineering Geology

• Chapter 20

La Conchita, California landslide. Photo from
the United States Geological Survey
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Land Use Planning Why?

• Safety?
• Is it the best use of a tract of land?
• Will the intended use be a misuse of the land?
• Are the resources required (water for example)
  for the intended use available?
• Is there a potential for pollution from this
  intended use of a tract of land?

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Conversion of Rural Land

• Between 1997 to 2001 2.2 million acres of rural
  land were converted to developed uses
• The rate of development is accelerating and the
  amount of available land has not increased
• Some lands will not support any or all forms of
  uses

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Land use in the United States
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Land converted to developed land
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Considerations in Planning

• What is the optimum use of a tract of land?
• We must consider
• Biological factors
• Ecological factors
• Geological factors
• Economic factors
• Political factors
• Aesthetic factors

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Land-Use Options

• Multiple Use using the same land for two or
  more purposes
• Parks or green areas used for recreation and to
  catch fresh water during a storm to allow it to
  infiltrate into the ground water
• Sequential use utilize the land for two or more
  different purposes, one after another
• Mines are used to provide the commodities found
  in the subsurface, then they are re-used for
  sanitary waste dumps, storage, or in-filled for
  parks

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Multiple land use
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Sequential Land Use
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Federal Government and Land-Use Planning

• Historically, federal lands are not equally
  distributed throughout the states
• Originally, federal emphasis was on resource
  development rather than preservation
• Federal lands fall into two categories
• Lands intended for preservation (national parks
  and wilderness areas)
• Lands intended for multiple use and compatible
  use such as grazing, logging, mining, exploration
  and drilling for petroleum (national forest)

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Land ownership by state, 1997
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Maps as a Planning Tool

• Land use planning requires abundant information,
  maps often provide much of the information
• Topography, bedrock geology, surface materials
  and geology, soils, depth to ground water,
  vegetation, population information, location of
  fault zones and flood plains, and more
• Maps can assist planners in long term planning,
  establishing restrictive zoning for earthquake or
  flood hazards, avoidance of other hazards as well

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Map representation of geologic considerations
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U.S. land-use classifications
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Maps as a Planning Tool

• Computers have aided planners
• Information required by planners is voluminous
• Computers have played an increasing role for
  planners to manipulate large volumes of
  quantitative information
• Geographic Information Systems (GIS) allow
  planners to manipulate the data to see and use
  what data is useful to a planning task while
  minimize, or obscuring, unimportant data
• GIS can allow a planner to see distinct layers
  of information that are important to the decision
  making process

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Digitized maps can represent data
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Composite map for land-use planning
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Engineering Geology

• Geologic factors and considerations vary
  depending on the site and the project
• A few considerations for a major project may
  include
• Rock types present in project area, are they
  uniform or variable
• Are they fractured or faulted?
• If they are, are the faults active?
• Is there a landslide risk?
• What types of soil or soils are present? Are
  they suitable for the project?
• What are the hydrologic factors? Surface and
  subsurface
• The list is nearly endless

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Failure of structure on unstable soil
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Relative magnitudes of loss of life and property
damage from various geologic hazards
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Engineering Geology

• Major projects often encounter major obstacles
• Alaskan Oil Pipeline Project (1300 km long)
• Spans a variety of geologic settings (rock types,
  structures, faults, slopes, soils, mountains,
  streams)
• Active earthquakes, seasonal flooding, animal
  migration routes all required solutions
• Climate factors North Slope is very cold with
  permafrost and a variable permafrost table

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Permafrost and permafrost table
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Differential subsidence of railroad tracks due to
partial thawing of permafrost
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Role of Testing and Scale Modeling

• Models are physically constructed (at a reduced
  scale)
• Models may be tested in a computer
• Failures of a variety of structures can be tested
  dams, bridges, or earthquake resistant buildings

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Scale modeling
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Case Histories

• Leaning Tower of Pisa the flow of the unstable
  soft clay layers
• Panama Canal Dipping layers of young volcanic
  rocks, lava flows, and pyroclastic deposits and
  dipping beds of shale and sandstone
• Bostons Big Dig Glacial sediments and weakly
  metamorphosed mudstone

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Geologic factors complicated construction of the
Panama Canal
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Bostons Big Dig Slurry walls keep excavations
from collapsing and nearby building foundations
from failing
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Dams - Failures and Consequences

• A catastrophic dam failure can impact many
  cities, thousands of lives, and cause millions of
  dollars worth of property damage
• St. Francis Dam coarse sandstones schists and
  mica-rich metamorphic rocks a fault
• Baldwin Hills reservoir an active fault zone
• Three Gorges Dam control the flooding, enhance
  navigation, and produce energy

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A regional overview of Hoover Dam
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Failure of the St. Francis Dam in California
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Benefits and issues in dam construction