Unit 1 Flashcards
What are the 4 core design professions and what are the general responsibilities of
each?
Engineering Utilities Streets Planning site characteristics market and fit Architecture product type style and materials Landscape Architecture Open space Site layout
List and briefly describe 5 locational considerations related to city form.
Survival based-basic formation: abundant water and food supply, ease of defense, favorable climate, plentiful resources
Economically based-early formation: transportation and trade linkages
Environment based-established city: fresh air, the country, avoid pollution, congestion, crime
Briefly describe the Urban Transect approach with regard to its purpose and
general form.
- Andres Duaney, New Urbanism
- Response to the clearly flawed “one size fits all” Euclidian zoning.
- Method borrowed from geography
- Shows a continuum of built environments ranging from rural to urban (natural, rural, urban, core, etc.)
- Recognizes the need for different standards in different types of built and natural environments
- Appropriate site design varies depending on where the site is located in the built environment
Why are soils important to site design? Provide three characteristics of soils that
are factors in site development
- Different types of foundations are needed for different types of soil
- Fertility of soil determines what a particular site can be used for
- Bearing capacity (how much weight the soil can handle. If a foundation is built on bedrock, for example, it can support much taller and heavier buildings than if it is built on soft soil)
- Infiltration (how much water and runoff the ground can handle)
- Permeability (how quickly the ground can absorb water and runoff)
- Other factors: erodibility, shrink-swell potential (related to bearing capacity), and septic waste absorption
List the slope guideline ranges and briefly describe the impact of each on
development.
- 0-.5% no drainage, slope must be altered to provide drainage
- .5-1% no problem: ideal zone
- 1-3% ok for residential, slight problems for large commercial areas
- 3-5% major problems for commercial, industrial, large-scale residential
- 5-10% special design needed, higher cost and risk
There are ideal development slopes. Developers will try to flatten site out to meet ideal slope
Explain the term “cone of depression.” What is the primary cause? What are the
potential large-scale effects?
• Effect that a well has on the surrounding water table
• Well output exceeds the aquifer’s recharge capacity
• Results in a suction effect that lowers the water table surrounding the well
Problems
• Can dry up smaller wells or natural water features nearby which cannot reach down to the lower water table and therefore dry up.
• In coastal areas, can result in saltwater intrusion and contamination of the groundwater supply.
Solutions
• Dig deeper wells
• Reduce rate of withdrawal
• Coastal areas-use injection wells to create a pressure gradient and force the saltwater out
What conditions (both human-caused and natural) typically combine to cause subsidence in populated areas?
- Subsidence-lowering of the ground level elevation due to changes underground
- Natural: earthquakes, faultlines
- Human-caused: overpumping of water, oil, and gas (fracking, etc.)
- Overuse of aquifers is a primary cause of subsidence in populated areas. As aquifers dry up, the resulting lowered water pressure causes drainage from the surrounding soil. As the water drains, the soil compacts, resulting in a sunken area above the aquifer.
What are 4 impacts of urbanization on stormwater related to stream discharge?
- Less infiltration
- Less interception-plant material
- More runoff
- Lower baseflow-on a daily basis
- Additional non-point pollutants-coming from all sources, eg. antifreeze.
What is the coefficient of runoff? List the range at which it measured with the
approximate coefficient of runoff for 2 typical ground level conditions.
Coefficient runoff-how much stormwater is running off depending on infiltration and permeability
0=full absorption, 1=no absorption
.05 sandy soil .13-.17 lawns .60 - .75 Multifamily housing .90 industry .95 asphalt
Name four advantages that centralized water and sanitary sewer service provide to
US communities.
Both centralized water and sanitary sewer services allow for higher density and efficiency since all residents use the same system (as opposed to septic systems).
Since all homeowners collectively pay for water and sewer services, the overall cost for individuals decreases, as does the need for maintenance.
Properly managed centralized water service is a boon to public health: it mitigates disease outbreak of waterborne pathogens, assures safe and quality water, and is a means to address certain health problems (eg. introducing fluoride for healthier teeth).
Centralized sewer systems assure that effluent is properly treated and disposed of. It allows for more quality control than private septic systems.
Name four causes of septic system failure and briefly explain.
Inappropriate soils-some soils, like clay, do not absorb much water and so cannot treat/dispose of effluent
Biological mat-saturation, too much effluent in soil
Bedrock near surface-fractures in bedrock allow untreated effluent to slip through rock, entering water table and contaminating supply
Water table near surface-soil must be dry to kill pathogens, bacteria travels greater distances in wet soil. Also, if soil is already saturated with water it is difficult to force more water (ie. effluent) into it
Briefly describe the primary characteristics of rights-of-way/easements as related to site development.
Easements allow government agencies (and private entities) to use private land for public purpose. The land is still owned by a private party but the other party can operate equipment, alter the landscape, and generally utilize a specific portion of the site. Storm water and utility easements are common; in these cases a municipality or power company would hold the easement.
Rights-of-way are easements that allow the public to travel across private property and are primarily used for roadways. Easements can impact site development through factors such as maintenance, cost, and layout (accommodating public access).
Briefly describe what causes a Combined Sewer Overflow (CSO), one of the two
ways they can be corrected, and what the primary benefit and primary negative in
correcting them are.
Combined Sewer Overflow occurs after major rain events when system capacity is overwhelmed. It results in raw sewage draining directly into rivers.
The main means by which CSO can be corrected is through separating storm and sewer systems into two physically distinct networks. This dramatically improves the health of urban rivers and minimizes the public health risk posed by CSO. The main drawback is the prohibitive cost of installation and maintenance of two separate systems, as well as the amount of time it takes install (years or even decades for a large system).
Briefly explain the link between septic systems and urban sprawl.
Unlike centralized sewer systems, septic systems require lots of land per resident. This limits the density at which developers can build and results in light density suburban or rural developments beyond the centralized systems of urban areas. Typically, the dividing line between high density urban areas and low density sprawl follows the outer limits of centralized sewer systems.
Name the diagram used to indicate the change in discharge of a stream over time,
and draw a simple example.
The Stream Hydrograph
Draw it
