nature + the city: site considerations

When people don’t interact with nature, they’re not inspired to take care of it. An entire generation of Americans grew up in the suburbs (myself included), isolated from the nature that their homes have covered with manicured lawns and impermeable pavement. Such a disconnect from nature makes people complacent in its invisible destruction – trash simply goes “away,” and the damage of auto emissions goes unnoticed by the human eye. For this reason, cities must incorporate nature within their borders to be sustainable not only in the tangible sense – nature provides vital ecosystem services like storm water management, air pollution mitigation, the list goes on – but also in the intangible sense, in that interaction with nature will drive urban residents to live in a more ecologically conscious way. This week, I’ll explore some ways to embody urban nature and what natural features to consider when planning our cities.

physiographic province

In order to lend urban residents a sense of identity, planners must create a sense of place, starting with the natural features around them. The physiographic province is a division of land area that shares similar features, climate, and geology. Physiographic provinces are what we all learned about under a simpler name – regions of Virginia – in the third grade, and our state’s include:

  • Coastal Plain
    • Geologically, the easternmost area is composed of layers of sand, clay, marl, and shell, and it stretches from the coast to the fall line. Lots of groundwater is available, but the potential for pollution is high due both to the geology and to the area’s high population density.
  • Piedmont
    • The largest province has a varied geology of igneous, sedimentary, and metamorphic rock formations as well as a range of groundwater quality and supply levels. Its border with the Coastal Plain exists at the fall line, and it encapsulates both of my cities of residence (Richmond and Charlottesville). Richmonders settled where they did because the fall line prevented ships from going any further, and now the city has embraced its riverfront as its greatest natural asset.
  • Blue Ridge
    • The province containing the Blue Ridge Mountains stretches only four miles wide in some areas, and impervious rock makes for low groundwater supplies.
  • Valley and Ridge
    • The V&R consists of sedimentary rocks like limestone, which makes for a high pollution potential because groundwater can flow quickly.
  • Appalachian Plateau
    • The water in the Appalachian Plateau, also called the Allegheny Plateau or the Cumberland Plateau, has largely been polluted by coal mining operations. Mine drainage acidifies the water to the point that it’s no longer usable.

physiographic provinces

Here are some photos of Virginia's physiographic provinces from Ian McHarg's seminal 1969 book Design With Nature.

Here are some photos of Virginia’s physiographic provinces from Ian McHarg’s seminal 1969 book Design With Nature.

watershed

We hear all the time about the James River watershed or the Chesapeake Bay watershed, but what really constitutes a watershed? A watershed is an area where all of the water draining off of the land goes into the same place, and there are watersheds within watersheds. These maps show the major watersheds of Virginia (where water flows into the Atlantic Ocean, the Chesapeake Bay, the Mississippi River, or the North Carolina Sounds) and the next-largest denomination. Within the James River watershed, for example, there are numerous watersheds inside where water flows into tributaries, and those watersheds are also divided into countless smaller watersheds.

Major watersheds

wshedboundaries

The boundaries of a watershed are found on its ridge lines, or the high points of the land where water flows in the opposite direction on each side. Cities or important parts of cities are often located on ridge lines, because it’s simply more convenient – less flooding to worry about. Charlottesville’s West Main Street, which connects the Rotunda and the City Courthouse, lies on a ridge that divides the city into two watersheds: Meadow Creek to the north and Moore’s Creek to the south. Here’s my markup of the ridge lines in Charlottesville.

photo (5)

ecotone

The roots of the term ecotone, the word ecology and the Greek –tonos, literally suggest a tension between two environments. However, an ecotone is an area where two environments meet in a biologically rich setting. Ecotones can occur at the macro scale, like the meeting of the Piedmont region and the Blue Ridge Mountains, or the micro scale, like Meadow Creek and its shores in southern Charlottesville.

When I think locally of ecotones, I think of the Richmond Riverfront Plan’s proposal for riparian terraces along the James River. The plan seeks to capitalize on our city’s greatest natural asset and bring people into contact with urban nature, but in designing for ecotones it’s important to prioritize the well being of the rich ecological landscape that exists there. Designs for terraces in Manchester hope to vegetate the currently cemented floodwall area with non-woody riparian species to add habitat space and decrease erosion.

Proposed terraces along the James River in Richmond allow for active and passive recreation among natural habitat that offers ecosystem services like water filtration.

Proposed terraces along the James River in Richmond allow for active and passive recreation among natural habitat that offers ecosystem services like water filtration.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s