GEOG 346: Day 15

Green Infrastructure

Housekeeping Items A reminder that the field trip assignment is due on

Thursday. For those of you who haven’t read the selection from

Randall Arendt, please do so: Conservation Design for Subdivisions by him and Holly Harper (1996; library on-line version: pp. 124-135). It will be on the exam

I have mentioned Charleson Park in Vancouver last time. Here are some pictures:

Vegetated walkway over a busy street

‘Business as Usual’ Infrastructure Hard infrastructure consists of roads, water

mains, storm sewers, and sanitary sewers. This chapter focuses mainly on storm sewers and alternatives thereto.

The more sprawl there is, the more infrastructure has to be paid for, and typically development cost charges (DCCs) don’t pay for these.

The infrastructure deficit for Canadian municipalities, as noted by Condon and others, exceeds $125 billion.

‘Business as Usual’ Infrastructure The consequences include: instead of much of the

water being absorbed and infiltrating, and thereby feeding groundwater and interflow to streams and rivers, it runs off into storm sewers loaded with contaminants;

it also increases sediment loading in water bodies and greatly increases streambank erosion

there is a loss of fish habitat – for instance, salmon habitat;

‘Business as Usual’ Infrastructure Further consequences

include: people are alienated from

nature and can’t see fish spawning;

the “urban heat island” effect is made worse.

With roofs, parking lots, streets and roads, driveways, sidewalks, and patios, imperviousness can reach close to 100% in urban areas.

Condon’s Alternative “Green infrastructure” for roads and stormwater

drainage. He doesn’t focus as much on municipal water and sanitary systems, though others have.

He starts out by arguing that conventional stormwater systems are a disaster because they abuse water, the most important element, he argues, of any ecological system.

Condon’s Alternative As natural drainage systems become urbanized, they

begin to see immediate degradation – even once they reach a point of 10% imperviousness. The greater the percentage, the worse it gets.

Imperviousness has a number of negative effects vis-à-vis the hydrological cycle.

Nanaimo’s Reality

In Nanaimo, it’s business as usual, as new forested areas – as parts of Linley Valley West, Oliver Woods, and Nelson Woods get paved over to accommodate roads and low-density subdivisions.

Condon’s Alternative In the U.S., the passage of the Clean Water Act in 1972

was a victory for water quality but, as Condon points out, not necessarily for water quantity, which is equally essential to the health of the hydrological system.

In 1999, the U.S. Fish and Wildlife Service made use of provisions in the Endangered Species Act to declare five species of Pacific salmon “endangered” and mandated that they be protected against logging and urbanization activity.

In Canada, the closest comparative piece of legislation is the Fisheries Act under the administration of Department of Fisheries and Oceans. However, the Conservatives have gutted the Act.

Condon’s Alternative Both cities and

salmon tend to favour the same areas – areas with a low grade (for salmon 1 - 4°). As a result, Vancouver has lost all but two of its sixty salmon-spawning streams over the last century and a half.

Condon’s Alternative Condon wants to emulate, as much as possible, a natural

drainage system where a maximum of 10% of all rainfall runs off, and he cites numerous examples where this has been partly achieved. Key elements would include:

narrow roads, possibly with porous shoulders smaller building footprints, and riparian buffers with continuous tree cover.

Green roofs could be a part of this, but he emphasizes that green roofs in the absence of a comprehensive stormwater management plan are of limited value.

He feels retention ponds are of limited value in that they may overflow and only filter 50% or less of pollutants.

Condon’s Alternative A key element is a minimum 30-metre setback from all

streams and watercourses. This has the benefit of shading fish-bearing streams, providing fallen logs – places for fish to hide – and corridors for wildlife to use. In Nanaimo, the minimum is 15-metre and much of the time it is disregarded without penalty.

Condon’s Alternative His more detailed ground rules are: infiltrate, infiltrate, infiltrate design for one inch of infiltration per day (Amble Green in

South Surrey manages 4 inches – equivalent to a 100-year flood event)

infiltrate everywhere possible, and don’t neglect that heavy soils can be a part of the solution.

Condon’s Alternative He also notes that soil management practices need to

change. Typically, soil is scraped off a site prior to development.

He advocates stockpiling it, avoiding compaction, covering it so it doesn’t wash off, and then re-applying it.

He also advocates using permeable paving surfaces where load-bearing surfaces are required, as we have already discussed.

Condon’s Alternative Vancouver has a “country lane” program. It also

has gravel shoulders on some streets.

Condon’s Alternative Condon spearheaded an alternative stormwater management

system in East Clayton, Surrey, but the city engineers made the developer put in a back-up conventional system for risk protection which removed all financial incentive for future developers.

In addition to alternative stormwater systems, eliminating combined sewer overflows (CSOs), as still exist in parts of Vancouver, is a must.

Friedrichstrasse Block 6 stormwater system in Berlin

Bioworks for sewage treatment in Kolding, Denmark

Daylighting Thain Creek – Before and After

                                                                            The Cheonggyecheon stream in Seoul, Korea was formed during the Joseon Dynasty in order to provide drainage for the city. It lasted for hundreds of years until the 1940s, when the city became so populated that a shanty town popped up around the stream and began polluting the area. The stream was gradually covered over with concrete, and by 1976 a 5.6 km elevated highway was built on top of it.Considered an example of ‘successful industrialization and modernization’, the highway remained there until 2003, when city planners tore it down to revitalize the area and help Seoul remake itself as a modern environmentally friendly city. The Cheonggyecheon Restoration Project took two years and cost around $281 million, but it has created a thriving stretch of green public space in the middle of the city.

Read more: Seoul Transforms a Lost Stream Into an Urban Park | Inhabitat - Sustainable Design Innovation, Eco Architecture, Green Building