Study Guide Ch. 5 Opportunities and Constraints

Question 1

Watershed

Answer 1

Land area that contributes surface water to given location and is defined by surface topography

Composed of subwatersheds (typically ranging in size from a few to several square miles)

Question 2

Watershed boundaries

Answer 2

Occur along ridges and water flows from these high points into valleys and other low points (such as rivers), with ridges dividing watersheds or areas within a watershed. This process defines the watershed boundary

Question 3

Subwatersheds

Answer 3

Composed of a group of catchment areas (usually measured in acres)

Typically ranging in size from a few to several square miles

Question 4

Time of Concentration

Answer 4

Amount of time needed for water to flow from the most remote point in a watershed to the watershed outlet (or a given point inside a watershed)


Note that the most remote point in the watershed is not necessarily determined by distance, since overland and channel flow time is dependent on slope, surface, and channel characteristics

Question 5

Evapotranspiration

Answer 5

Evaporation occurs on land and water surfaces
Transpiration from plants also returns water to the atmosphere
May recycle as much as 50 percent of precipitation back to the atmosphere and the rate of evapotranspiration depends upon numerous factors, most notably climate

(i.e., evapotranspiration occurs at a much higher rate in dry, hot conditions than it would in a cold humid climate)

Question 6

Surface runoff

Answer 6

Precipitation that runs off the land’s surface and flows downhill.

Precipitation, soil type, slope, and vegetation all influence the amount of surface runoff.

Example: areas with low-permeability soils, steep slopes, and large areas of impermeable paving will have more surface runoff than areas with highly permeable soils, gentle slopes, and little paving

Note that runoff will flow from the site’s high point to the site low point following the prevailing site topography

Water always flows perpendicular to the direction of the contour line

Question 7

Recharge

Answer 7

Water that infiltrates the lands’ surface and percolates downward to the underlying water table, the upper surface of groundwater

Areas with high-permeability soils, minimal slope, and sparse vegetation have the highest recharge rates.

Question 8

Groundwater

Answer 8

Subsurface water flow that discharges to streams, lakes, wetlands, or the ocean.
Under normal conditions, this discharge is called “base flow”

Question 9

Riparian Corridor

Answer 9

A riparian zone or riparian area is the interface between land and a river or stream, and the riparian corridor is the area that encompasses a river or stream and the land adjacent to it, with some sources defining the outer extent of the corridor as the area within the streams mean flow during the raining season or during normal precipitation events.

Note that erosion in riparian systems occurs on the outside bank of the river, whereas the sediment deposition occurs on the inside bank of the river.

Question 10

Water Table Depth

Answer 10

Varies between sites and surface water features (e.g., lakes) form in those situations where the water table is higher than the land below it.

Question 11

High water tables constrain development in several ways:

Answer 11

- prevent adequate site drainage, including groundwater recharge
- preclude the use of septic systems (in areas not connected to a sewer system)
- complicate subsurface excavation
- require waterproofing for building foundations and subsurface structures (e.g., basements)

Question 12

Floodplains

Answer 12

The area of land adjoining a body of water that has been or may be covered by floodwater. Flooding occurs within the floodplain.

Areas that accommodate floodwaters in excess of channel capacity by storing floodwater, thereby reducing peak flows downstream.

Are a “pressure-relief valve” for the channel by regulating the increase in stream energy in the channel

Question 13

Floodplains, and flood risk, are delineated

Answer 13

By the frequency with which they are likely to flood

100-year floodplain: an area of land that has a 1% chance to flood in any given year.

Question 14

The extents of floodplains can be determined by looking at four key variables:

Answer 14

- topography
- soils
- vegetation types
- extent of past flood flows

Question 15

Flood Insurance Rate Maps

Answer 15

Produced by FEMA

document floodplains and special hazard areas throughout the US

Question 16

Upstream development impacts floodplains how

Answer 16

Reduces the amount of previous surface that can absorb precipitation, more water is forced downstream during weather events, and a x-year flood can become a x-year flood with correspondingly higher chances

50-year 2%
25-year 4%

Question 17

Floodplains are composed of three areas

Answer 17

- channel
- floodway
- flood fringe

Question 18

Channel

Answer 18

The portion of the floodplain where a stream/river flows under normal conditions

Question 19

Floodway

Answer 19

Portion of the floodplain that is used to convey floodwaters during a 100-year flood

Question 20

Flood fringe

Answer 20

The portion of the floodplain outside of the floodway that does not convey floodwaters and usually contains slow-moving or standing water

Question 21

Base Flood Elevation (BFE)

Answer 21

Whole-foot elevations of the 100-year floodplain that have been studied in detail at selected intervals.
In areas where building has occurred within the 100-year floodplain, BFE calculations are often used to determine the height to which living spaces must be constructed to be safe from a 100-year flood.

Question 22

Freeboard

Answer 22

And portion of the flow in excess of the base flood elevation (measured in feet)

Question 23

Building within 100-year floodplain according to LARE

Answer 23

Buildings should not be placed inside the boundaries of the floodplain

You should choose uses that do not require erecting any structures on site (e.g., golf courses, recreational uses, gardens)

Question 24

Flood hazards are exacerbated by the presence of

Answer 24

“Hard” engineering structures such as levees and riprap

They simply redirect flood energy further downstream and often result in increased stream bank erosion

Question 25

Flood hazards are best mitigated by:

Answer 25

- expanding opportunities for stormwater infiltration
- minimizing the uses of impervious surfaces
- decreasing the volume of runoff during storm events
- through restricting development to areas outside of floodplains
- replacing “hard” engineering structures with “green” infrastructure (e.g., live plant/willow cuttings) that slows water velocities along the channel

Question 26

Soils well-suited for stormwater infiltration

Answer 26

Highly permeable soils
Containing large ratios of sand and/or larger material such as gravel

Question 27

Soils poorly suited for infiltration

Answer 27

Clay soils known for their low permeability

Question 28

Used to elucidate specific characteristics on a site

Answer 28

Vía a soils test
Existing uses (e.g., industrial contamination)
Vegetation (e.g., presence of acid-loving plants)
Hydrology (e.g., erosion patterns, ponding/slow drainage)

Question 29

Siting rural developments and soil percolation

Answer 29

Sites with a slow rate of percolation cannot accommodate septic systems, and these areas often preclude the development of housing or other uses that might require a septic system (where a municipal sewer system is not present)

Question 30

Permeability

Answer 30

Rate at which water moves through soil

Question 31

Infiltration rate

Answer 31

The rate of speed at which water flows into soil through small pores

Question 32

Percolation

Answer 32

The downward movement of water in a soil

Question 33

Expansive Soils

Answer 33

Soils that swell when exposed to large amounts of water and shrink when the water evaporates

Typically contain large ratios of clay

Best method is to find alternative construction site

Question 34

Ground heave

Answer 34

Upward movement of the ground usually associated with the expansion of clay soils that swell when wet

As the soil generally cannot expand downwards or sideways, the result is that the exposed upper surface of the soil rises up (and is therefore the opposite of subsidence)

Question 35

Liquefaction

Answer 35

Takes place when loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking (e.g., earthquakes)
Makes solid soils behave like liquids
The greater the soil density, the lower the liquefaction risk, therefore dense, clay soils tend to have a much lower risk of liquefaction

Question 36

Differential Subsidence

Answer 36

Subsidence occurs when the soil beneath a building is unstable and sinks downward
Differential occurs when two points settle at different rates
Several causes but within LARE be aware that placing a single structure across two separate soil profiles could cause differential subsidence to occur

Question 37

Settlement

Answer 37

Downward movement of the ground caused by the weight of a structure

Question 38

Landslides

Answer 38

Caused by a number of factors including heavy rainfall, unstable soils, extreme topography, loss of vegetation and construction activity

Regulations typically prevent construction on sites that are vulnerable to landslides, and geotechnical engineers are often employed during the design process to determine landslide risk on a site, as well as any necessary mitigation measures (e.g., catch walls, diversion ditches)

Note that roads and major circulation pathways should never be placed in areas prone to landslides and areas with highly erosive soils

Question 39

Damage by earthquakes is exacerbated by

Answer 39

- building height (i.e., taller buildings are more susceptible to earthquake damage)
- hillsides, ridges and steep topography
- proximity to major fault lines
- placing structures parallel to the anticipated direction of seismic waves

Question 40

Most important factor in determining a site design

Answer 40

Site topography

Question 41

Affected by the topographical features on a site

Answer 41

- building location
- road alignments
- pedestrian circulation and safety
- stormwater management

Question 42

Site planning and design should follow or otherwise relate to existing landforms to

Answer 42

Respect context
Grading causes significant site disturbance and is costly

Question 43

Site elevations impact:

Answer 43

Drainage patterns
Visibility

Question 44

Elevation both on a site and in the surrounding landscape determines

Answer 44

Size and spatial configuration of local viewsheds

Question 45

Elevation data is generally shown in two different ways on topographic maps

Answer 45

Spot elevations
Contour lines

Question 46

Spot elevations

Answer 46

Highly accurate readings shown for specific points

Often areas of importance to designer (e.g., finished floor elevation of structure, top or bottom of wall) or to the understanding of the landform (e.g., high point of hill, summit of mountain)

More accurate than information provided by contour lines

Question 47

Contour lines

Answer 47

Lines on a topographic map that establish the elevation at any given point along that line

Contour intervals (vertical distance between each contour line) will vary according to the accuracy of a map, but the elevational information provided by the contour line is generally considered accurate to one half the contour interval given

If a map provides 2-foot contour intervals, that map would be considered accurate to one foot

Question 48

Topographical information can be used to

Answer 48

Determine the intensity of a slope

Question 49

Closely spaced contour lines

Answer 49

Indicate steep slope

Question 50

Contour lines that are widely spaced indicate

Answer 50

A gentle slope

Question 51

Contour line can also indicate the “signature” of a landform

Answer 51

Ridges are identified by contour lines that point downhill

Valleys/Swales are identified by contour lines that point uphill

Question 52

Character of slopes

Answer 52

0-3% nearly level
3-7% gently sloping
7-12% moderately sloping
12-25% strongly sloping
25-40% steeply sloping
40-70% very steeply sloping
70%+ extremely sloping

Most sources identify 2% as the minimum slope necessary for a site to shed water and have proper drainage

Question 53

Slope Analysis

Answer 53

When mapped onto a site, slope percentages can be used to conduct a slope analysis
Used to identify steep and unbuildable slopes and to identify the possible location for building sites and access (e.g., roads, walkways, etc.) as well as for stormwater management

Usually a graphic representation of slope shown in classes or ranges, with these ranges corresponding to (or precluding specific site uses)

Question 54

Slope Aspect/Orientation

Answer 54

Direction that the slope faces relative to the sun

Aspect is typically described by compass direction (e.g., a northerly aspect) and - along with slope - impacts the amount of solar radiation received at a given location on a site

For example, orientation toward the sun may influence a building’s energy use and performance, and it helps determine what types of vegetation can be planted in specific areas (e.g., sun, part sun, shade)

Question 55

Military Crest

Answer 55

Refers to the point on a hill just below the top of the hill that offers greatest visibility of the slope below

Question 56

Relief

Answer 56

The relative difference in elevation between two or more points

Question 57

Microclimate

Answer 57

Site-scale variations in climate due to topography, vegetation, and orientation, among other variables

Micro-climatic conditions comprise the vast majority of climate-related subject matter on the Section 3 exam

Question 58

Southern slope receive

Answer 58

The most sun in winter months

Question 59

Southeastern slopes

Answer 59

Offer the most desirable microclimates

Question 60

North-facing slopes are colder

Answer 60

Than south-facing slopes

Question 61

Western slopes are

Answer 61

Hottest in the summer

Question 62

Cold winter winds

Answer 62

Blow from the northwest

Question 63

Cooling summer breezes

Answer 63

Blow from the southwest

Question 64

Water features (e.g., lakes) mitigate

Answer 64

Climate extremes (i.e., they act as a heat sink in winter and provide cooling effect during summer)

Question 65

Hot, arid

Answer 65

- avoid heat-absorbing materials (e.g., metal) and large exposed glass surfaces
- use walls to create favorable microclimates
- deflect hot,dry winds with earthworks, screening and walls
- prevent heat build-up in structures through the use of thick walls
- use a drought-tolerant plant palette
- use pergola and trellis structures on south and southwest walls
- provide shade in outdoor areas, but position them such that they allow
for winter sun

Question 66

Hot, Humid

Answer 66

- avoid using solid walls and earthworks that block cooling winds
- use high canopy trees and open planting patterns to maximize evaporation and cooling winds
- provide shade structures with high ceilings/venting

Question 67

Temperate

Answer 67

- promote shade and evaporative cooling during summer months
- block winter winds without disrupting summer wind patterns
- locate uses and structures along a southern orientation (from SSE to SSW) to promote solar gain in winter

Question 68

Cold

Answer 68

- locate uses and structures along a southern orientation (from SSE to SSW) to promote solar gain in winter
- avoid northern entrances to site and buildings
- block winter winds with mixed deciduous and evergreen plants
- use earthworks, walls or structures to divert cold NE/NW winter winds
- promote cooling summer winds
- provide afternoon shade during summer months using deciduous trees

Question 69

Urban heat island effect

Answer 69

Occurs when natural land cover is replaced by dense concentrations of pavement, buildings, and other surfaces that absorb and retain heat

This effect increases energy costs (e.g., air conditioning), air pollution levels, and heat-related illness and mortality

Note that surface albedo (the ability of surfaces to reflect sun energy) plays an important role in urban heat islands, with dark surfaces absorbing and storing heat and light surfaces reflecting heat energy back into the air

Question 70

Key urban heat island points

Answer 70

- dark roofs are significant contributors to the urban heat island effect
- dark asphalts absorb more heat energy than concrete
- green roofs can be used to mitigate urban heat islands (and roofs can be painted white to reflect solar energy)
- vegetation and water can be used to mitigate urban heat islands
- tree canopy cover can play a significant role in reducing surface temperatures in urban environments

Question 71

Note that although this phenomenon is considered to be negative

Answer 71

The urban heat island effect does provide a beneficial warming effect during winter months in extremely cold climates

Question 72

Urban-wildland interface

Answer 72

Areas where human development abuts undeveloped land

Present the highest potential for wildfires because urban uses introduce a variety of fire catalysts (e.g., cigarettes, grills, etc.) and are exposed to any baseline fire danger that already exists in these “wild” areas

Question 73

Fire danger is determined by the following three variables

Answer 73

- existing fuel load (the amount of flammable organic material in an ecosystem)
- weather
- topography

Question 74

Best fire management practices entail

Answer 74

Proactive removal of fuel and creating a landscape that provides a fire-resistant buffer surrounding all structures

Question 75

Fire resistant buffer divided into

Answer 75

1. Building protection zone
2. Building buffer zone
3. Natural area fuel reduction zone

Question 76

Building Protection Zone

Answer 76

Located 30 ft from all sides of a structure

Either be free from vegetation or contain only low-growing, fire-resistant plant species

Site furnishings should be constructed of nonflammable material (e.g., metal, stone) and gravel, recycled glass, or other nonflammable material should be used instead of bark mulch.

Fire departments will often provide a list of plants suitable to be planted within this “defensible space” and they advise against planting trees near houses because trees can create a “fuel ladder” effect in which fire climbs up the tree (from the ground), thereby igniting the structure. Landscape maintenance should reduce the structure’s vulnerability to fire dangers and allow easy access for fire suppression equipment if an emergency arises

Question 77

Building Buffer Zone

Answer 77

Extends from the edge of the building protection zone to all areas within 100 ft. of a structure

Well-spaced and pruned trees are allowed within the building buffer zone. Trees and shrubs should be spaced at least 10 ft. from one another, as measured from the edge of crown. Plants should be removed in density is too high, although pruning can also be used to maintain spacing in certain instances. Any tree branches that are within 6 ft. of the ground or one-third of live crown height (whichever is greater) from the ground should be removed to discourage the “fuel ladder” effect. Landscape maintenance should be conducted as often as necessary to maintain the spacing and branch structure described above.

Question 78

Natural Area Fuel Reduction Zone

Answer 78

Extends indefinitely beyond the building buffer zone, with the goal of reducing the available fuel load by removing debris, brush and dead branches that accumulate over time.
Although fire management maintenance in this zone is conducted less frequently than in the other two zones, many of the same principles still apply. As in the building buffer zone, trees in the natural area fuel reduction zone should be pruned to prevent “ladder fuel” formation, and selective pruning should be used to address unsafe conditions.

Question 79

Carrying capacity

Answer 79

Measure of the type and density of development that can be supported without detrimental effects to society, the economy, or the environment and without decreasing the capacity of the environment to sustain these uses into the future.

Question 80

Habitat fragmentation

Answer 80

The breaking up of a continuous habitat into smaller patches with diminished ecosystem function and less biodiversity

These changes affect the movement of the organisms (especially migration) and can alter ecosystem characteristics to the extent that they no longer support native vegetation and wildlife

Question 81

Patches

Answer 81

Fragmented habitats

Question 82

Corridors

Answer 82

Areas that connect patches

Question 83

Gaps

Answer 83

Areas between patches that are not connected by a corridor

Typically possess little ecosystem value

Question 84

Size of patch and the distance between patches correlate to ecosystem impact

Answer 84

Larger patches and those located closer to one another tend to support greater biodiversity and improved ecosystem function

Question 85

The best way to preserve biodiversity is to

Answer 85

Avoid activities that cause habitat fragmentation

Question 86

Large, contiguous natural areas - especially riparian corridors and wetland areas - should be given the

Answer 86

Highest priority for protection from development

Question 87

Existing corridors require protection to help

Answer 87

maintain biodiversity and ecosystem connectivity

Question 88

Habitat restoration is most effective when

Answer 88

It addresses gaps in existing corridors

Question 89

Many animal species need more than one habitat type for different life cycle stages, such as

Answer 89

Reproduction and migration

Question 90

Wetlands

Answer 90

Fragile ecosystems
Unnecessary excavation and grading can disrupt groundwater flows that feed into them, causing irreparable harm
Heavily reliant on watershed management and are exceptionally sensitive to “upstream” changes in a hydrological system

Question 91

For LARE wetlands

Answer 91

No construction should ever occur inside wetlands (or - if forced to choose - the proposed use should be the least disruptive) and stormwater should not be drained into wetlands without being sufficiently treated for quantity/volume and quality

Question 92

A wetland will confer the following benefits to a site and its users

Answer 92

- groundwater recharge and discharge
- sediment stabilization
- flood attenuation
- water quality maintenance
- wildlife habitat
- climate moderation
- shoreline protection

Question 93

Wetlands are defined by their

Answer 93

Hydrology
Soils
Presence of specific vegetation (namely, hydrophytes)

Question 94

US Fish and Wildlife Wetland Classification System defines five major wetland types, and they are as follows:

Answer 94

1. Marine (open ocean and its associated coastline)
2. Estuarine (tidal waters of coastal rivers, salty tidal marshes, mangrove swamps, and tidal flats)
3. Riverine (rivers and streams)
4. Lacustrine (lakes, reservoirs, and large ponds)
5. Palustrine (marshes, wet meadows, fens, bogs, swamps)

Note that salt marshes are generally considered to be the most important, productive and diverse of all ecosystem types. Situated at the interface between land and sea, and salt and freshwater ecosystems, salt marshes offer habitat and food to a wide variety of terrestrial and aquatic life

Question 95

Bog

Answer 95

Type of wetland found in northern climates that is characterized by acidic soils, rich deposits of organic material (such as peat) and a diversity of vegetation types.

Note that bogs and fens are identical with the exception that bogs are fed by rainwater, whereas fens are fed by groundwater

Question 96

Estuary

Answer 96

A semi-enclosed coastal body of water connected with the open sea. Estuaries are strongly affected by tidal action and contain brackish water (seawater is mixed with fresh water from land drainage)

Question 97

Littoral Shelf

Answer 97

A shallow area in a water body that is planted with native aquatic vegetation normally located by an outflow or at the waterline/shoreline of a constructed wetland or stormwater management structure. Plantings located in the littoral shelf are used to filter out the nutrients and improve water quality.

Question 98

Marshes

Answer 98

Type of wetland characterized by herbaceous vegetation no taller than 6’

Question 99

Swamps

Answer 99

Type of wetland dominated by woody vegetation

Question 100

Acidification

Answer 100

Occurs in water due to excessive carbon dioxide or the presence of sulfur and nitrogen compounds that dissolve in the water.
Occurs due to air pollution or as a large-scale process related to global climate change

Question 101

Eutrophication

Answer 101

Is the over abundance of nutrients (e.g., nitrogen, phosphorous) in water, leading to excessive plant growth (typically algae)
Often results from fertilizer runoff from agricultural lands or residential yards

Question 102

Noise

Answer 102

Generally travels by line of sight and dissipates over distance

Comprises the volume/intensity of the noise, the nature of the noise source, the height of the noise source in relation to the elevation/height of the site, the material characteristics of the surrounding area (i.e., vegetated and soft surfaces tend to absorb noise, whereas hard, paved surfaces tend to reflect noise) and the presence of (or lack thereof) sound shielding or barriers

Noise-sensitive uses should be built as far from the noise source as possible, and, if possible, noise-reducing barriers should be placed between the noise source and the site in question

Question 103

If conducting a noise analysis on a site, the landscape architect should record three key items:

Answer 103

- source and type of the noise
- direction and distance that noise travels from the source
- duration and intensity of the noise

Question 104

The effectiveness of any noise barrier will depend upon five factors

Answer 104

1. Distance
2. Height
3. Continuity
4. Length
5. Mass

Question 105

Distance to the noise source

Answer 105

Noise barriers should be constructed as close as possible to either the noise source or to the receiving location in order to maximize noise diffraction

Question 106

Height of the barrier in relation to the noise source

Answer 106

At minimum, barriers should be built to a height such that they block the line of sight between source and receiver

Question 107

Continuity of a barrier

Answer 107

A single, continuous barrier is more effective than multiple, fragmented barriers because noise will penetrate any gaps in a barrier

Question 108

Length of a barrier

Answer 108

The length of a noise barrier should generally be 1-2 times the distance between the source and the barrier to minimize sound diffraction that would otherwise travel around the barrier to the receiver

Question 109

Mass of the barrier

Answer 109

Barriers with greater mass have a greater impact on noise mitigation.

For example, a 6’ tall earthwork is a better noise barrier than a 6’ tall brick wall because the earthwork has considerably more mass than the brick wall

Question 110

Most important considerations when designing a noise control feature

Answer 110

Acoustic effectiveness
Cost
Visual attractiveness

Question 111

Surface texture impacts noise diffraction

Answer 111

A smooth surface reflects sound more than a textured surface

Question 112

Vegetation makes a relatively poor barrier to noise

Answer 112

If plantings must be used as a noise barrier, the density of the plant (densely branched plants are better at blocking noise than plants with an open branch structure) and its foliage type (evergreen foliage will dissipate noise throughout the year, whereas deciduous plants would only offer seasonal benefit)