Green Infrastructure Glossary - GreenBlue Urban
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Green Infrastructure Glossary


The capacity of a development project to adapt so as to respond to changing social, technological, environmental, and economic conditions.

Air Rights

A type of easement granting permission to a developer or constructor to build over a street or other structure.


Aesthetics or other features of a development that increase its marketability or usability to the public.


“American National Standards Institute” writes specifications and standards for many professions and products through committees of experts in that field (i.e. nursery standards, planting stock, etc).


A fully enclosed or semi-enclosed rectangular court surrounded by a single building or between buildings that is open air.

Back Lot Parking

Parking that is contained behind buildings, in the middle of a block, linked yet hidden from the pedestrian’s experience of a street.


Refilling the planting hole, done after the tree has been stabilized.

Balled & Burlapped

Planting stock that has been dug from the field and wrapped in burlap (held in place by twine or a wire basket) in order to keep the soil ball intact during transport and before installation. Abbreviation B&B.

Bare Root

Planting stock that has the soil removed from the root system. The root system must be kept moist at all times to ensure that the roots don’t dry out and die.

Base Plan

An essential agenda showing site boundaries and significant site features, used as a basis for subsequent plan development.


The process of making visual improvements to a streetscape or entire urban area, most often involving tree planting and other greenery, but also including decorative or historic-style street lights, old-fashioned cobblestones, etc.


Vertical columns used to physically block or visually guide vehicular traffic in an area. They can be removable for ultimate versatility, or permanent.

Branching Habit

Structure of a tree, relating to what the branch attachments look like (wide angle vs. narrow, included bark, etc.).

Build Form

The shape of developments including buildings, and other structures, not only individually, but collectively. How buildings relate in terms of height, scale, and character determines the extent to which they will define the public realm.


The required placement of the front of a building relative to the street right-of-way, to ensure an appropriate street or open space enclosure. The objective of a build-to-line is to maintain a consistent street wall along the edge of a streetscape.

Building Codes

Regulations specifying the type of construction methods and materials that are allowable on a project.

Building Permit

An authorization issued by a government agency allowing construction of a project according to approved plans and specifications.

Built Environment

The man-made creation of or alterations to a given area, in contrast to the “natural environment.”


Widened sidewalk areas at intersections, often in place of on-street parking, thereby narrowing the pedestrian crossing distance over a right-of-way.


“Computer Aided Design and Drafting” is a digital design process in which computers are used to help produce precise drawings and details for the construction of a project.


The diameter of the trunk measured 6 inches above ground for stock up to 4 inches in caliper size. If larger than 4 inches, caliper measure at 12 inches above the ground.


Wounds to a tree caused by biotic or abiotic conditions that penetrate the bark, causing it to spilt open. The vascular tissue and the bark are often destroyed or rendered useless by cankers. Cankers are often circular or oval in shape, and can increase in size if attacked by the pathogen repetitively or if the tree cannot seal them over and environmental conditions around them do not improve. Wounds provide entryways for decay causing pathogens to enter and weaken the structure of the tree.

Central Leader

A continuation of the main tree trunk located more or less in the center of the crown, beginning at the lowest main branch and extending to the top of the tree. Also referred to as the dominant leader.


Yellowing of the leaves due to nutrient deficiency, usually nitrogen or iron (not occurring at fall leaf drop).

Circling Roots

One or more roots whose diameter is greater than 10% of the trunk caliper circling more than one-third of the trunk.

City Development Plan

A consultative process that examines a city’s current situation and development challenges to create a long-term vision for development and a medium-term action plan that includes specific projects.

Compacted Soil

Soil that has increased in bulk density due to heavy foot or motor traffic, or intentionally as a structural base for building upon. Roots cannot penetrate into compacted soil because it is so dense, and compacted soils often become waterlogged or starved for oxygen which further impacts tree growth.


The size, form, and character of a building element relative to the streetscape and other elements around it. This may be determined by the size and proportion of windows in a building façade are usually related to one another, the spaces between them, and the scale of surrounding buildings.


The protection, improvement, and use of natural resources according to principles that will assure the highest economic or social benefits for people and the environment now and in the future.

Conservation Plan

A documented strategy for conserving and protecting various natural or manufactured resources. Such a plan is used as a management tool in decision making regarding soil, water, vegetation, and other resources of a particular site.


The form of the landscape. Contour lines are map lines connecting points of the same ground elevation and are often used to depict and measure slope and drainage.

Corner Treatment

A unique built feature on a corner building that acknowledges its prominence on the street in terms of views and architectural presence. Can be achieved by adding prominent streetscape elements, and articulating building elements such as a turret or by subtracting from the building volume resulting in conditions such as recessed entries.

Cost Benefit Analysis

Study of the potential cost of site purchase, demolition, and improvement in comparison to the income or other benefit to be derived from site development.


The portion of the tree beginning at the lowest main branch extending to the top of the tree.

DBH (Diameter at Breast Height)

A standard method of expressing the diameter of a tree trunk or bole of a standing tree.


The floorspace of a building, or buildings, in relation to the streetscape or given area of land.


Death of living tissues, usually leaves and twigs first, that progress from the outside or top of the tree towards the interior or base.


The running off of water from a land surface or subsurface, such as through sewers or natural means.


The legal grant of right-of-use to an area of designated private property.


A branch of biology dealing with the relationship between living organisms and their environment.

Encircling Roots

Roots with erratic growth that form tangentially or circularly around the base of the tree’s trunk. Also referred to as Tangential Roots.


The use of buildings to physically define public spaces particularly through proportions between height and width in an area to create places that are comfortable to pedestrians.

Environmental Impact

The change to an area’s natural resources, including animal and plant life, resulting from use by man. Some projects may require conducting of an “environmental impact assessment” before development can proceed.

Environmental Impact Assessment

A study that examines whether an infrastructure project is disruptive to the natural environment, in both the short and long terms, with the purpose of developing strategies to mitigate negative externalities and encourage positive design elements.

Fine Roots (Fibrous Roots)

Primary roots usually less than 2mm thick that have the function of water and nutrient uptake. They are often heavily branched and support mycorrhizas. These roots may be short lived, but are replaced by the plant in an ongoing process of root turnover.

First Order Roots

The first tier of roots branching off from the stem, usually being the oldest roots on the tree. In young plants, the first order roots should be the about the width of a pencil.

Frost Canker

A canker caused by rapid temperature changes during winter days. Often starting as split bark, it provides an entry way for pathogens and subsequent decay.

Frost Crack

A vertical split in the bark and wood of a tree due to rapid temperature changes during winter days, which can open and close depending on the air temperature. There is a major difference between a frost crack and a frost canker. A crack penetrates into the structural wood, not just the other living tissues.


Locations where a significant number of people enter and exit downtown. They occur at a variety of scales, including to downtown as a whole, to precincts, or to specific streets or open spaces.

Gateway Treatment

A design feature intended to signify entrance to a distinct area, usually a place where a new character or sense of identity should be acknowledged. Achieved through details of the built form, or through landscaping and signage.


The slope of a plot of land. Grading is the mechanical process of moving earth to change the degree of rise or descent of the land in order to establish good drainage and otherwise suit the intent of a landscape design.

Grand Avenues

Gateways into the downtown defined by their generous public realm treatments. Buildings along these should be a little ‘grander’ than most, in the sense that they will have careful attention to the building quality and articulation.

Green Infrastructure

A water management approach that protects, restores, or mimics the natural water cycle in an effective and economical way that enhances community safety and quality of life. It entails planting trees and restoring wetlands, rather than building a costly new water treatment plant.


A strip of unspoiled, often treed, agricultural or other outlying land used to separate or ring urban areas.


The act of straightening a tree by pulling it into the vertical position. Underground guying is the most unobstrusive method for supporting large rootballed trees, and has many advantages over staking.


Elements added to a natural landscape, such as paving stones, gravel, walkways, irrigation systems, roads, retaining walls, sculpture, street amenities, fountains, and other mechanical features.

Heritage Conservation

Refers both to saving significant buildings, retaining parts or places that are valued for their heritage contribution, and to enhancing the meaning and quality of life in a specific place by maintaining its uniqueness, and supporting the cultural and economic vitality that accompanies areas with strong conservation.

Human Scale

The impression of a building when seen in relation to its surroundings, or the size and proportion of parts of a building or its details, that relates in a positive way to the visual and physical experience of a pedestrian.

Impact Fee

A mechanism to directly shift the cost of infrastructure from the government to a private sector developer, whose project stands to benefit from a public investment.

In-Fill Development

The development of vacant parcels in urbanized or suburbanized areas, typically bringing the density of the area closer to that allowed by the existing zoning regulations.


The systems and networks by which public services are delivered to citizens, including water supply, sanitation, energy, and transportation networks.


A dysfunctional root system where the roots curve back towards the surface in a “J” like pattern.

Kinked Root

A main root that is sharply bent.

Landmark Frontages

Locations which are prominent because of their context, such as adjacency to a public open space or important street, or because of their content, such as heritage resources or public art. These are closely related to gateways.


The main shoot off which most of the growth occurs.

LEED Certification

“Leadership in Energy and Environmental Design” is a system of measurement which rates new buildings (or their plans) on their level of energy use and environmental consideration. It is meant to encourage new developments to become more energy efficient and environmentally sensitive.


“Low Impact Development” is a term used in North America to describe a land planning and engineering design approach to manage stormwater runoff. LID emphasizes conservation and use of on-site natural features to protect water quality.

Main Roots

The largest diameter mother roots typically growing from the trunk or main taproot that form the main structure of the root system.

Master Plan

A preliminary plan showing proposed ultimate site development. Master plans often comprise site work that must be executed in phases over a long time and are thus subject to drastic modification.

Media / Medium

The mixture of bark, peat, sand, compost, wood, and other organic matter used to grow plants. Also referred to as substrate.

Mixed Use

A mix of uses within a streetscape, building, or other particular area; possibly including employment, residential, commercial, or retail.

Modal Split

How the total number of journeys in an area or to a destination is split between different means of transport, such as train, bus, car, walking and cycling.

Mulch Volcano

The act of piling mulch in a mound around the base of a tree to a point where it looks like a large volcano. This is not healthy for the tree and can create an environment suitable for the growth of pathogens and insects.


Having more than one leader. Leaders can come from the ground (as in clump birches) or start part way up the tree.


Dead areas in the leaves; they are brown and brittle.


An urban node is a place where activity and routes are concentrated, often used synonymously with junction.


A tree node is a raised ridge of wood, from which each year’s growth begins. Previous growth is woody whereas the current growth is not. Nodes from the past few growing seasons can be seen.

Open Space

A relatively clear or forested area left untouched in or near a city. It may be active open space, such as a baseball field, or passive open space, such as an area of natural woodland.


A road laid through a garden or park-like landscape, usually with median and roadside tree plantings.

Pedestrian Orientation

The characteristics of an area where the location and access to buildings, types of uses permitted on the street level, and storefront design are based on the needs of pedestrians.

Permeable Paving

Hardscape material containing open voids between particles that allow water and air movement through the paving material, contributing to the growth of healthy urban trees through the admission of vital water and air to their rooting zones.


Sugar and other carbohydrates that are produced by a tree’s foliage and stems during photosynthesis.

Primary Streets

Active for all modes of transportation, but have less vehicular traffic than avenues meaning they are the most balanced downtown streets. Used to move people within the downtown.


The act of growing a plant from cutting, graft or seed.

Propagation Depth

The depth at which a tree was positioned in the first nursery planting.


Any attempt to restore to beneficial use land that has lost its fertility and stability; most often applies to mining reclamation, such as the restoration of strip mines and quarries.


The substantial demolition, redesign, and then rebuilding of a project site area.

Reduction Cut

Cutting a stem or branch back to a live lateral branch that is typically oriented away from the central leader, also referred to as a subordination cut.

Removal Cut

Removing a branch back to the trunk, or removing a secondary branch from a main branch.

Right-of-Way (ROW)

A strip of land, including the space above and below the surface, that is platted, dedicated, condemned, established by prescription or otherwise legally established for the use of pedestrians, vehicles, or utilities.

Root Ball

The ball of soil the planting stock is purchased with that contains the root system.

Root Ball Shaving

Removing the outer substrate and roots on the periphery of the root ball, typically done before site planting using a sharp blade or saw.

Root Flare

The base of the trunk where it meets the root system. Flares appear as the tree ages. Also referred to as Trunk Flare.

Root Heave (Pavement Heave)

Lifting and/or cracking in hardscape surfaces caused by tree roots colonizing immediately under the paved surface and as the root diameter increases, the flatwork is raised.

Root Plate

The combination of roots and soil close to the trunk that holds the tree erect in the landscape.

Secondary Street

Streets used to access destinations within downtown, rather than to access downtown itself.


The minimum distance from the edge of the street at which a building must be built.

Shared Space

An urban design approach which seeks to minimize the segregation of pedestrians and vehicles. This is done by removing features such as curbs, road surface markings, traffic signs, and traffic lights.

Site Plan

A dimensioned drawing indicating the form of an existing area and the physical objects existing in it and those to be built or installed upon it.


The natural elements with which landscape architects work, such as plant materials and the soil itself.

Soil Structure

The architecture of the soil. A well-structured soil functions like a reservoir, enabling trees to accept, store, and transmit water, nutrients, and energy, while also providing room in which roots can propagate.


The act of propping up a tree with stakes and attachments including ropes and webbing. Potential liability from exposed stakes makes it a less preferred method to “Root Ball Guying”.

Stem-Girdling Roots

Roots with erratic growth that form tangentially or circularly around the base of the tree’s trunk. As the tree and the roots grow and come into contact with each other, the root will cut off the flow of nutrients from the roots to the trunk by girdling the tree.

Step Back

A recess of taller elements of a building in order to ensure an appropriate built form presence on the street edge. Usually articulated at the top of the building base.


Planting material sold at a nursery.

Street Side Parking (On-Street Parking)

Parking that lines the side of a street, usually parallel or angled.

Street Wall

A condition where buildings consistently line or front onto the edge of a street. Best achieved where buildings have consistent setbacks built out to the sidewalk.

Street Wall Elements

The combined components that give a street wall its unique character, such as recessed entries or bay windows or signage treatments or canopies.


The visual elements of a street, including the road, adjoining buildings, street furnishings, trees, and open space, that combine to form the street’s character.


Response of a tree to outside factors including insects, pathogens, pollution, soil compaction, etc. Results can be slowed/stopped growth, stunted leaves, etc.

Structural Roots (Anchor Roots)

Large roots that have undergone considerable secondary thickening and provide mechanical support to trees.


“Sustainable Urban Drainage System” is a natural approach to managing drainage in and around properties and other developments. SUDS were developed in the UK and work by slowing and holding back the water that runs off from a site, allowing natural processes to break down pollutants.

Surface Roots

Roots that proliferate close below the soil surface, exploiting water and easily available nutrients. Where conditions are less than optimum at deeper depths, the growth of surface roots is encouraged and they commonly become the dominant roots. Without proper root management, this commonly causes pavement heave problems in urban trees.

Sustainable Development

Development that considers the long-term environmental, social, financial, and maintenance needs of a project before investing in it. A project should be able to meet the needs of the present without compromising the ability of future generations to meet their own needs.

Sustainable Infrastructure

The designing, building, and operating of urban infrastructure in a way that does not diminish the social, economic, and ecological processes required to maintain human equity, diversity, and the functionality of natural systems.


Forcing plants to break dormancy by layering them with plastic, mulch and water, then leaving them in a warm environment. “Water Bags” can often have this effect.

Tap Root

The primary, typically large diameter root that emerges from a seed.

Thinning Out

Removing branches throughout the tree.


The lay of the land, particularly its slope and drainage patterns; the science of drawing maps and charts or otherwise representing the surface features of a region or site, including its natural and man-made features.


Occurs between buildings to help create continuity and cohesiveness in a streetscape, with buildings that are beside each other, across the street from each other, or are otherwise part of a building grouping which has design elements that reference one another. Can be articulated through a wide range of design elements (i.e. overall building height, massing, setback, materials etc.)

Transplant Stock

A period of time the tree takes to recover from root loss. Generally the larger caliper the tree, the longer the transplant shock.

Urban Grain

The pattern of the arrangement and size of buildings and uses and their plots in an area, usually along a street. Fine urban grain refers to a pattern of street blocks and building sites that is small and frequent, thereby creating a dynamic and animated urban environment for the pedestrian.

Urban Structure

The shape of a downtown as a whole, including its overall height and density, street wall heights, setbacks/build-to lines, and distinct functional and character areas. It builds on existing and historic development characteristics, and considers linkages and interfaces with the surrounding context.


The process in which populations shift from rural areas to cities. The term usually describes the situation where the proportion of the total population residing in cities or towns is increasing.

Vascular System

The area in a tree where water and nutrients flow to and from the roots/leaves. This area is located in the juvenile wood- between the bark and the heart wood (nonliving center of the tree).

View Corridors

The long, straight streets in a downtown and in the surrounding neighborhoods with direct views.

Visual Terminus

The end point of a view corridor. Often accentuated through design elements such as landscaping, tree planting, and public art.


A condition of a system of routes which are barrier free, interesting, safe, well-lit, comfortable and inviting to pedestrian travel.

Watering Bag

Irrigation bags (or watering bags) are a slow release watering system that fit around the base of a tree’s trunk to deliver a high volume of water directly to the root system of a newly planted trees. However, they do not provide proper ventilation and can promote fungus and disease in the tree trunk.


Tools which orient users of an area to ensure the ability to navigate through an area. These include signs, graphic communications, spatial markets, streetscape elements, building design, and the street network.


A shared space concept developed in the Netherlands where pedestrians and cyclists have legal right-of-way over motorists.


“Water Sensitive Urban Design” is a land planning and engineering design approach which integrates the urban watercycle including stormwater, groundwater, and wastewater management and water supply, into urban design to minimize environmental degradation and improve aesthetic and recreational appeal.


A legal form of land-use control and building regulations usually exercised by a municipal authority; usually involves setting aside of distinct land areas for specific purposes, such as commercial, educational or residential development.