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121 Cards in this Set

  • Front
  • Back
What has caused the profound change in the rate and amount of runoff reaching streams and rivers
This change is due to land development
– Both urbanization and agricultural development have increased surface runoff
• Property damage from floods increased
• Water quality reduced
• Channel erosion accelerated
• Habitat degraded
• Riparian environment compromised
How can the reactions to the existing problems with runoff can worsen the problem
– Political and engineering reactions are not always the right path to take
• Corrective measures can be more damaging than problems they remedy
• Streams ditched and piped underground
• Wetlands drained
• Dams erected
• All at great expense!
What are some examples of responsible land use planning with regard to runoff?
requires a management approach
– As opposed to trying to “control” it
– Assess the changes in runoff brought on by earlier land development
– Formulate development plans that provide analytical forecasts of changes in hydrology brought about by the proposed plans
Four Ways to Dispose of Precipitation
1. Interception – precipitation is taken up on the surfaces of vegetation
2. Infiltration – direct absorption into the soil
3. Depression storage- collects on ground and in small hollows
4. Runoff or Overland Flow
What is the process that Runoff or Overland Flow goes through
o Begins as sheetflow
o Its capacity to infiltrate the soil is controlled by:
 Intensity and duration of rainfall
 Prior wetting of the soil
 Soil texture
 Slope of the land
 Nature of vegetative cover
o Sheetflow concentrates into tiny channels called rills
o Water further concentrates into narrow channels called gullies.
o Ultimately it joins streams or rivers, lakes or wetlands
How does landscape control runoff
– Forested landscapes retain the most precipitation and yield least runoff
– Barren or lightly vegetated landscapes, natural and human made, produce the most runoff… especially developed landscapes!
– Aside from climate … land cover, soil composition and texture, and slope are factors of greatest concern in stormwater planning
What is the Coefficient of Runoff
• This represents the proportion of precipitation available for overland flow – or runoff.
• A dimensionless number, this can be assigned to a surface.
• For urban areas, this number is a function of the impervious surface cover.
Computing Runoff for Planning Purposes
• The rational method can be used to estimate runoff in a small watershed
• It is based on:
– The coefficient of runoff
– Precipitation intensity
– Area of the watershed
• This method may be used to determine peak discharge in a channel
• It may also be used to solve for total volume of discharge in a watershed during the course of a storm
How have land use changes in the U.S. led to an increase in both amount and rate of runoff.
– Larger and more frequent peak flows
– Increased flooding and flood hazard
– Damage to aquatic environments and water quality
What does it mean that there has been an increase in Amount and Rate of Overland Flow (Runoff) due to urban development?
• Increases in the coefficient of runoff with increased urbanization
– Farmlands may have double the runoff of natural landscapes they displaced
• Decreases in the concentration time of runoff
– Pipes and ditches more efficient (faster) stormwater removal system
What are some examples of Stormwater Mitigation in Development Planning
• Most communities have enacted strong stormwater management standards on new development
• The goal is zero net increase in stormwater discharge from a newly developed site
• So, the peak discharge for a design storm can be no greater than before development
• These strong standards pose a dilemma:
• New development does increase runoff
• At the same time the new development needs to be protected from stormwater
What are some examples of good Storm Water/Runoff Management Strategies
1. Plan development so it produces little or no increase in discharge (site adaptive planning)
2. Return excess water (stormwater) to the ground (source control)
3. Store excess water on or near the site and release it slowly (basin storage)
Things to consider for Stormwater/Runoff Site Adaptive Planning
• Define sites with good hydrologic performance – land that is capable of infiltrating and holding stormwater
• Surface materials need to be considered, avoiding impervious surfaces wherever possible.
• Facilities should be clustered, allowing more land to retain a natural cover
What is Stormwater Source Control
• Disposing of stormwater at or near its point of origin
– This usually involves some form of soil infiltration
– Accomplished onsite by directing stormwater to:
• Vegetated areas
• Shallow depressions
• Troughs
• Pits
What are some examples of Commercial Source Controls for runoff
Parking lot into landscape strip
Roof drain into drywell
What is Basin Storage
• Directing stormwater to a holding basin
– Then releasing it slowly over time
– “Shaves” the peak discharge and reduces the rapid rate of stormwater delivery to streams
– Usually involves the construction of detention basins
• These ponds can be unsightly, expensive and dangerous in residential areas (they need to be fenced)
Things to consider for Comprehensive Water Management Planning
• The environment’s multiple components tend to become isolated and subsequently addressed individually by modern land planners
• Water is the one theme that is central to virtually all landscape planning.
– Water management planning can unify the rest of a landscape plan
• But water planning must be addressed through the watershed and its drainage net
The Watershed of a site
• Every planning site is nested within a drainage system
• Principles that govern watersheds also apply at smaller site scales
Steps for Building a water management plan
• Pinpoint project location in the drainage system
• Determine the opportunities and constraints both up and downstream
– Flood risk
– Water supply
• Then search for complementary water systems and how to integrate them compatibly:
– Stormwater systems &
– Wetlands
• Allowances must be made for wetland watersheds in planning - Protect Wetlands by Protecting Their Watersheds
How do you protect wetlands
by protecting their watersheds
What are Drainage Networks
• A drainage network is a system of channels from rivulets to riverbeds
• The network is formed much like the branches of a tree (dendritic)
• It encompasses the entire network of waterways feeding water to a drainage basin or watershed (last lecture)
– A general rule of thumb, the size of the main channel increases with the size of the drainage basin
How Development Alters Drainage Networks
• Development makes artificial channels
• Changes size and shape of natural systems
– Both the above changes have serious environmental consequences
• Increased flooding
• Loss of aquatic habitat
• Reduced water supplies at low flow periods
• Degraded water quality
What are some examples of Land Use and Abuse with regard to drainage networks
• Drainage networks are given little consideration as geographic entities in land use planning
– A site’s location in a drainage network is often ignored
– Community planners ignore implications of retention basins and other facilities built to “deal” with the problem of stormwater
How to Map and Analyze Drainage Networks – Stream Orders
• The principle of stream orders describes relative position, or order, of a stream in a drainage network – a branching phenonema
– This principle may also be used in describing the organization of non-natural systems, like irrigation and storm-sewers
– The principle helps us understand the relationships among streams in complex flow systems
– Sizes of streams range from first order, the smallest, to 12th order, the largest (the Amazon)
Bifurcation Ratio
• The number of streams of a certain order that combine to form the next order averages 3 – this is called the bifurcation ratio
• Receiving channel must be at least three times the average size of the tributaries
• Stream numbers decline with increasing stream order
– Therefore, first order streams are most numerous in any drainage basin
• The number of streams of a certain order that combine to form the next order averages 3 – this is called the bifurcation ratio
• Receiving channel must be at least three times the average size of the tributaries
• Stream numbers decline with increasing stream order
– Therefore, first order streams are most numerous in any drainage basin
Ordering Drainage Basins
• We can also rank drainage basins using the stream order principle
• First-order are those emptied via first-order streams
• Second-order emptied via second-order streams
• Fifth-order emptied by a fifth-order trunk stream
• This is referred to as a nested hierarchy
What is a Non-Basin drainage area
• This area contributes directly to higher order streams in a large basin
• It can be 15 to 20% of the overall area
What are some of the Land Use Alterations of Small Drainage Basins:
Agricultural and Non-Urban Alterations
• Deforestation, grazing and crop farming initiate soil erosion and gully formation
• Gullies advance and expand the drainage network
• This increases the number of first order streams AND the drainage density
• Road building, lumbering, commercial agriculture have the same effect as above uses:
– All require construction of drainage ditches – or first order streams
What are the Results of Higher Drainage Density
• The main consequence is shortened concentration times as channel flow is much faster than overland flow
• Discharges are larger as shortened concentration times fall closer to the peaks of rainstorm intensity
– Therefore, large flows occur with higher frequencies
What is Urban Development’s Effect on Drainage Networks
• Natural channels are “pruned”, or parts are removed
– Replaced by ditches and storm sewers
• Net effect is an increase in total number of channels and an increase in overall drainage density
– Coupled with lower infiltration rates from impervious cover, these changes lead to:
• Increased amounts of runoff
• Shorter concentration time
• Larger peak discharge
– In the end, magnitude and frequency of peak discharges are increased for receiving streams
• Storm sewers are pipe systems
– Work on gravity flow
– Usually constructed of concrete
– Capable of conducting water at a rapid rate
• Four times that of natural channels
– Increases frequency of urban flooding by six fold
What are the Planning and Management Considerations for drainage networks?
• Watershed planning must address small basins since they are the building blocks of larger systems
What are watershed zones
1. Outer contributing area – generates the most flow
1. Runoff
2. Groundwater
3. Interflow
4. Overland flow
2. Collecting zone or low area – where water from contributing area accumulates
3. Central conveyance zone – valley and stream channel where water conveyed to higher stream orders
What does Each Watershed Zone Require Different Planning and Management Strategies?
1. Contributing zone is least susceptible to drainage problems
• Less up-slope drainage
• Surface flows small
2. Collection zone has serious drainage problems
• Seepage
• Ground water saturation
• Subject to inflooding
3. Edge zone between 1 & 2 requires different strategies
• Where convex, dry along the axes
• Where concave, has funnel-like patterns of runoff and wet along inner axes
4. Central Conveyance Zone
o This zone includes the main stream channel and valley, including a small flood plain
 There is baseflow from ground water most of the year
 Stormwater is responsible for peak flows, floods
 Least suited to development off all zones
What are the Watershed Planning Implications
• Development guidelines:
– Identify:
• Buildable land
• Open Space
• Special use areas
• Density of land use
– % of impervious surface defines
– Greater the density, greater storm flows
What is a Drainage Basin Carrying Capacity
• This would be the amplitude and type of development that a basin can sustain without degradation of:
– Water features
– Water quality
– Biota
– Soils
– Land use facilities
• 30% density is suggested as a “rule of thumb” but the author states this is “highly questionable”
What causes Waves
• Oscillations in water due to force of friction from wind blowing across water surface
• Waves travel horizontally, but most movement of water itself is vertical, up-and-down
What causes breakers to form (waves)
• Near a coastline the seafloor slopes upward –
– Wave base intersects ocean floor and friction builds
– Wave pushes water up as it slows and waves pile up from behind
– When wave height exceeds 7X wavelength, it forms a breaker
• There is only horizontal movement of water from breaker to beach, called surf - an erosional agent
What is Wave refraction
• Bending of a wave
• Causes waves to arrive nearly parallel to the shore
What are the Consequences of wave refraction
– Wave energy is concentrated against the sides and ends of headlands
– Wave energy is spread out in bays and wave attack is weakened
– Over time, wave erosion straightens an irregular shoreline
What moves sand along the beach
Waves that reach the shoreline at an angle cause the sediment to move along a beach in a zigzag pattern called beach drift
Why wave movement is perpendicular to the shoreline
• Waves seldom approach the shore straight on, but rather at an angle
• When waves reach shallow water with a smoothly sloping bottom they are bent and tend to become parallel to the shore
What are the basic input/output systems of the Long Shore Sediment System
– Three basic parts:
• Sediment sources
– Streams and rivers
– Shore erosion (may involve the loss of expensive coastal real estate)
• Transport zone
• Sediment sinks
– Places where the longshore system loses its energy and deposits its load of sediment
» Leeward sides of islands
» Mouths of bays and harbors
What is gross and net sediment transport
– Gross sediment transport
• Transport direction may change with storms and the seasons
• There can be reversals in the transport system
– Net sediment transport
• The balance between directions sediment is moved
• In So. CA waves from the NW quadrant of the compass determine net transport and it is a large movement trend
– Sediment balance (site-scale)
Evidence of Long Shore Sediment System being out of balance
• This system is rarely in balance in nature, even less so when humans are involved
– Note the spit that exists at the entrance to the harbor, formed due to longshore current that transports sediment, from west to east (left to right), along the outside edge of the breakwater. Sediment is constantly dredged to keep harbor open.
Coastline Planning Applications
• Beaches actually expand and contract
• In general, data isn’t kept on sediment mass balance
• In planning, we must resort to interpretation of old records
– Maps
– Aerial Photos
– Land Survey Records
Factors that contribute to shoreline features
• Features vary depending on several factors including
• The rocks along the shore
• Currents
• Wave intensity
• Whether the coast is stable, sinking, or rising
Shoreline • Features caused by wave erosion
• Wave-cut cliffs
• Wave-cut platform
Shoreline Features associated with headlands
• Sea arch
• Sea stack
retrogradational or retreating shoreline features
• Sea arch
• Sea stack
• May be caused by erosion
• Rise in water level
• Subsidence of coastal land
Progradational coastlines
caused by deposition of sediment
Features related to beach drift and longshore currents – prone to rapid changes in shape and volume
• Spits
• Elongated ridges of sand extending from the land into the mouth of an adjacent bay
• Often the end of a spit hooks landward in response to wave-generated currents
Features related to beach drift and longshore currents
• Baymouth bar – a sand bar that completely crosses a bay
• Tombolo – a ridge of sand that connects an island to the mainland or another island
What are Barrier Islands
• Elongated bars of sand that form parallel to shore
• Likely formed from sand deposited on continental shelf during last glaciation – waves and wind shaped sand
• Lagoons with mudflats form behind barrier islands
• Mudflats develop into vegetated salt marsh
What causes Sand Dune Formation and Nourishment
• Depositional landform associated with windblown sand
– Dunes exhibit a characteristic shape with three components:
• The backslope or windward surface
– Shallowest slope between 10° and 15°
• The crest or highest point of dune
• The slip face or leeward slope where deposition occurs
– Steepest slope between 30° and 34°
What is a Dune Field
• One of the most prized development locations of all coastlines, dune fields depend on two key factors:
– An ample supply of erodible sand
• Furnished by the beach in front of the dune field
• A lesser source is wave cut banks and cliffs
– A source of wind energy to drive the sand landward
What is dune migration
• Initially tongues of sand migrate landward to form dunes
• Advancing edge of the dune deposit buries vegetation, soil and even wetlands
• Migrating dune forms an elongated U, growing longer and deeper
• At some distance inland, the onshore wind is weakened enough for sand movement to cease
Managing Dunes
• These are very attractive to residential, resort and recreational development
• However, they are extremely fragile environments
– Delicate balance between vegetation, sand deposits and slopes
– A small change in one can lead to a chain of changes… like erosion and dune movement
• Management is advisable that recognizes the changeable landscape of dunes
Human Impacts on Coastlines
• 50% of U.S. population live <60 miles from coastline
• Development pressure is huge along coastlines
• Development must be weighed with coastal sustainability in mind
Purposes behind coastal engineering
– Protecting shore & property from hazards
– Stabilizing & nourishing beaches
– Maintaining traffic & trade into ports
Evaluating land use proposals for coastal development
– Planners must first know makeup and dynamics of the coastline involved
– Systems critical to understanding:
• Direction of water and sediment movement
• Types of coastal landforms and lithologies
• Assessment of recent erosion and deposition trends
• Map trends of recent coastline change
• Identification of longshore systems followed by approximation of sediment budget
Key Questions for Planners (coastal development)
• What is nature of system of interest in terms of sediment movement and direction?
• What is relationship among features, processes and trends of coast?
Where is proposed project located in the system? What is its relationship to the forms and features of the system?
High-Risk Sites for coastal development
• Low elevation coastal terrain is generally not suitable for development
– Especially when exposed to the open sea
• This terrain should be left as open space
• Setbacks must be adequate to protect from hurricane driven erosion and flooding
– Unfortunately, supported by National Flood Insurance Program many homeowners are able to rebuild in these high-risk sites
Impact of Global Climate Change on Coastlines
• Planning for sea level change will add to the problems associated with coastal development
– Frequency and magnitude of storms will increase at the same time sea levels rise
• There are estimates of 5-35 inches – areas <5 ft elevation at greatest risk
• Planners will need to establish land use fallback positions.
– For sure, this problem will require a sizeable GIS army
the primary source of light and energy on Earth
What is Solar radiation an important factor in?
• Solar radiation is an important factor in environmental design
What is sun angle? What causes differences in it?
• Sun angle is formed by sunlight striking the earth’s surface
– 90° to 0°
• Higher the angle, the more concentrated (intense) the sunlight
• At a lower angle, same amount of sunlight must spread out and cover more area
• These differences in sun angle are due to the curvature of the earth
What are the Variations in Sun Angle Due to Seasons and Topography
• Earth’s axial tilt is responsible for the seasons
– The Earth’s axis is 23.5° off of perpendicular to the sun
– The highest and lowest angles of sunlight fall at the solstices
– Intermediate angle falls at Equinoxes
– Angles in the mid-latitudes (like us) vary 47° from high to low
How do you Calculate Sun Angle
• To calculate sun angle at noon, calculate the latitudinal degrees difference from your point of interest from the direct overhead sun location
– E.g., we are at 34° N and on Dec. 21st (our winter solstice) the direct overhead noon sun will be at the Tropic of Capricorn, at 23.5° S … 57.5° away.
– Subtract this amount from 90° to get our noontime solar angle (90° - 57.5° = 32.5°)
What causes Other Variations in Sun Angle
• On a local scale sun angle is influenced by:
– Slope (sometimes called aspect)
– Time of day
• Sun angle on the ground = SAflat +/- slope angle
To determine the amount of solar heating on any surface, that surface’s _____________ must be known.
What is Albedo
– Albedo is the reflective capacity of a surface
• Fresh snow may be 95%, blacktop 5%
What does Incoming solar radiation that is absorbed, not reflected, produce?
rise in temperature
What are the major differences in heat capacity for different surfaces
• Water has high specific heat, meaning it takes a lot of energy to heat it up and cools off slowly
• Wet sand likewise would take longer to heat
• Dry sand heats AND cools quickly
Land Use Implications for solar climate
• The impact of development on the ground level solar landscape is profound
• Important issues in roof design
• Color (dark vs. light-colored roofs)
• Angle
• Shade trees
• Green roof
• The difference in albedo may influence air movement at the surface as hot air rises, cooler air moves horizontally to fill the vacuum
Building Implications for solar climate
• Building placement can have more effect than hill slopes.
• Urban buildings create shadow corridors and small solar windows
• Plans for shade should be made in warmer climates or where summers are warm
– Trees are important here, they can reduce insolation by 50%!
Uses of Shade Trees
• Deciduous trees cool on south and west sides in summer, allow sun to reach inside buildings in winter
• Evergreen trees provide shade all year, and serve as wind breaks
• Street trees shade parked cars, protect homes from reflected heat
Health and Safety with regard to solar climate
• Shade is a distinct advantage in warm climates in the summer
• It can also encourage the build up of snow and ice in shadow corridors in the winter
• Living units with northerly exposures end up with cooler room temperatures and a higher risk for hypothermia for elderly residents
What is the Urban Climate
• When rural landscapes are displaced by urban landscapes, atmospheric changes near the ground produce a distinct climate type – the Urban Climate
– Warmer
– Less sunlight
– Less wind
– Foggier
– Polluted
What is an Urban Heat Island
• Energy flow is greatly changed by the effects of urban surfaces – we call this the “heat island” effect
What creates/causes a Heat Island
• Urban surfaces generate sensible heat at ground level
• Heat loss in the atmosphere is lower than in rural landscapes
• Combined this results in generally higher temperatures over urban areas
– Urban center develops the highest temperatures

Reasons for a Heat Island
• Street and roof materials have lower albedos, higher absorption rates than in the countryside
– These absorb heat faster, release it quicker and heat overlying air
• Lack of water, plants and soil means fewer water vapor sources
– Less latent heat released, more sensible heat
• In NYC, artificial sources (cars, industry) contribute more heat than the sun does
• Wind speeds in urban areas are also less, so there is less flushing of air
Air Pollution in urban climate
• Higher in the inner city than suburbs
• Pollution may also vary greatly in different quadrants of a city
– Site specific pollutants
– Short term boundary layer changes in mixing and flushing
– When the air is calm, pollutants build up over source areas
• Particulates are especially hazardous to human health and may form a visible dust dome
What is a Dust or Pollution Dome
• A large dome of warm air forms over urban areas
– This is the urban boundary layer
– High particulate backscatter can reduce radiation by 50%
• More CO2 absorbs more heat
Regional Issues of air pollution
• Plumes of polluted air may extend many miles beyond urban boundaries
• Acid rain is a problem in southeastern Canada and the northeastern U.S. caused by the formation of sulfuric acid in polluted air
• Nitrogen deposition has also become a problem in rural areas of California
– It actually fertilizes areas in our local mountains and deserts
What is Nitrogen Deposition? what effects does it have on the landscape?
• Nitrogen in the form of nitrogen oxides (NOx) and ammonium (NH4) is carried by the wind and deposited in high-elevation and also desert areas.
– Extra nitrogen can act as a fertilizer, causing unnatural changes to plants, animals, and water and soil chemistry in sensitive ecosystems.
What are the Land Use Implications with regard to urban climate
• Highway construction and the resulting sprawl has resulted in a new urban form, the edge city
– Build up near key interchanges around and between urban regions
– Foster even greater travel among commuters
– Trend to commute longer distances continuing
• There is incentive to reverse sprawl and increase urban density
– This reduces pollution, but only by 30% max
Fragmentation of North American landscapes (or habitats) has led to negative effects on ______________
What is biodiversity
– Biodiversity - the full range of variety and variability within and among living organisms and the ecological complexes in which they occur
– There are three levels of biodiversity
• Ecosystem or community diversity
• Species diversity
• Genetic diversity
What is Landscape Ecology
Landscape ecology is the application of spatial analysis to problems of habitat planning and management
What are mosaics
• Today, fragmentation has led to a “patchy” geographic appearance of habitat, termed “mosaics” … remnants of various habitat and ecosystem types
Why do we study Form, function, and change of ecosystems
• Form, function, and change of ecosystems – we study this to improve understanding and design landscapes that can better sustain biodiversity
What is the ultimate goal of landscape ecology
• The ultimate goal is to reduce fragmentation and restore functional patterns
What have Island biogeography studies shown?
• Island biogeography studies in the past revealed that biodiversity depends on both habitat area and the distance between habitats
1. The larger the “island” or patch, the more species it can support
2. The greater distance between “islands” the lower the genetic mixing and biodiversity
How do island biogeography studies apply to habitat fragmentation?
– Small remnants of original habitats behave like small islands
• They cannot perform biologically as the former intact habitat did
• A 90% reduction in habitat leads to a 50% biodiversity loss
– The further apart habitat islands are, the more mixing among “island” species falls
– With fragmentation, species numbers slowly decline… so long-term monitoring is called for
is the local environment of an organism – its “address”
is an organism’s way of life, or what it does in its habitat – its “job description”
Habitat versatility
humans (and rats and cockroaches) have a wide range of habitat versatility, but most organisms are not able to trade one habitat for another!
What are the drawbacks of Habitat Reconstruction
• Once a habitat is destroyed, it cannot be recreated to support all its organisms – there are simply too many subtle interactions with other organisms, insects and microflora!
• Wetland reconstruction is the most common habitat restoration to replace land destroyed/disturbed by development.
– Reconstructed wetlands are poor replicas of destroyed wetlands cannot support prior diversity
The Impacts of Land Use on Natural Habitats
• Effects of land use depend on type and density of use
• Light agriculture leaves much habitat intact and many corridors connecting various patches
• Roads and railroads further divide patches of habitat (imagine a beetle trying to cross the road)
• As demand for agriculture increases, wetlands are drained and farming takes place on steeper slopes… places that were left intact until then
– Dams built
– Woodlands removed
– Remaining habitat in small widely separated patches
What is Habitat Loss
• Simplification of habitat – farming reduces native flora and replaces it with biological “monocultures”
– This leaves just one or two crop species and hardy weed species (mostly introduced)
– Very little is left for the original species to survive on
– The original species are reduced or eliminated
• But a number of weedy species are favored by such changes
• They respond to edge environments (along roads) and disturbed environments
• “Weedy” mammals and birds are also favored by these simplified habitats
– Cowbirds, blue jays, crows, coyotes, opossums, rabbits, raccoons
What are Endangered species
– Endangered species are in imminent danger of extinction in all or a significant portion of their ranges
What are Threatened species
– Threatened species have rapidly declining populations and are likely to soon become endangered
What did The Endangered Species Act that was passed in 1973 focus on?
• The act focused on federal construction and land use projects and private projects that use federal money or need federal permits
What is The Umbrella Effect
• Protecting species isn’t all bad though…
• Protecting individual species can protect entire ecosystems… in an umbrella effect
• To protect individual species, their entire ecosystems must also be protected
• By default, a larger number of organisms and habitats will receive protection
What are Extinction Prone Species
Endemic species
Species with small populations
Island species
What are Endemic species
– Have ranges so small they are prone to extinction from a local disturbance
– Some are relict populations from earlier times
– Often have very limited habitat requirements
What are Species with small populations
– Loss of relatively few individuals may put the population below a critical threshold of a breeding population
– Genetic diversity falls and with inbreeding individuals become less and less fit for survival
– Small populations of a species that reproduces slowly are also at risk – for instance Cheetahs
What are Island species
– Evolve in a protected environment without predators and competition
– When non-native competition or predation is introduced, island species fare badly
Patterns and Measures of Landscape Fragmentation before settlement
• Before settlement, North America’s biological landscape was covered by an interlocking network of ecosystems
• These ecosystems were different sizes, shapes and compositions
• The basic structural framework for ecosystems was provided by the continent’s physiography
What was the terrain and fragmentation of US before development
• In New England, the forest was patchy where the Appalachian terrain was diverse and irregular
• In the Midwest the tall grass prairies were vast and uniform, like the landscape of the great plains
• Land use systems were superimposed on these terrains – some systems honored the original physiography but modern uses like highway systems treat the landscape indiscriminately
– Each land use system added a layer to the landscape, fragmenting ecological patterns of the original landscape
• Habitat patches became smaller and corridors between them became narrower and more segmented
What are the 5 Types of Habitat Corridors
• Riparian network
• Interfluve corridor system
• Linear corridors
• Grid corridor systems
• Segmented or disjointed corridor systems
What is a Riparian network
– This system has a fully linked structure following networks formed by stream systems – governed by the principle of stream orders
What is an Interfluve corridor system
– On fingers of upland terrain lying between riparian corridors
What are Linear corridors
– Along rights-of-way for utilities and roads… also seashores and lakeshores
What is a Grid corridor system
– By-products of the public land survey system (township and range), a rectilinear system of land use leaving corridors along property lines
What are Segmented or disjointed corridor systems
– Fragmentation of any corridor leads to these
What do habitat conservation planning programs focus on
• These programs all focus on open space
– Parks
– Wildlife preserves
– Wilderness areas
– Forest reserves
– Landscape quality
– This program emerged in 1982 as part of the Endangered Species Act
• It selects habitats for preservation within larger use areas – such as forests used for lumber
• Agreements are made between government and landowners
• These plans are binding for 50 years, no matter what new scientific evidence comes to light
Habitat conservation Approaches to Open Space
• Greenbelts – popular in Europe and No. America
– Usually part of park and recreation planning
– Stream corridors are popular for greenbelts
– Usually multiuse areas, but recently planners are focusing on habitat conservation and biodiversity protection
What are the major Barriers to Biodiversity in the Landscape
• Our Interstate Highway system is a major barrier to the flow of organisms and thus gene flow
– It becomes an ecological wasteland that limits seasonal migrations and interbreeding among divided populations
– These barriers may become more important as climate changes and populations must shift their ranges in response to global warming trends
– The ranges of many organisms in California may need to shift North as climate warms
What are the Bioplanning Guidelines
• Focus on habitat systems rather than selected species
• Focus on critical locations, such as lakes and wetlands in riparian corridors
• For sustainability, focus on a firm physiographic base
• Pay attention to habitat connectivity and plan to set aside larger areas with natural connections between them
Which landscapes retain the most precipitation and yield least runoff
Forrested Landscapes
Which landscapes produce the most runoff
– Barren or lightly vegetated landscapes, natural and human made, produce the most runoff… especially developed landscapes!