Crime Prevention through Environmental Design

There are many ways to prevent crime, and crime prevention through environmental design (CPTED) is the 'design or redesign of an environment'.

Regardless of the type of landscaping and planting designs applied, the fencing installed or type of plants used, if the property is not maintained to the standard of care for that property type, the image of 'neglect and lack of care' will speak directly to those who can use this weakness to trespass or commit crimes.  As a landscape designer, my objective in CPTED is to create physical space that considers the needs of the immediate users, the intended and expected functions for the space.  In this process, I also have the responsibility to predict behavior of illegitimate users and intruders.

There are three strategies I implement for security design; natural access control, natural surveillance and territorial reinforcement.  Natural access control strategies are intended to deny access to crime targets and to create a perception of risk to offenders.  Natural surveillance is those methods directed at primarily keeping intruders under observation.  Both of the natural methods can be accomplished through layout and site planning, creating or eliminating circulation.

Territorial influence is created by designing a cohesive feeling amongst neighboring and adjacent properties, creating a sense of proprietorship so that would-be offenders perceive that territorial influence.  Professional series low voltage lighting featuring LED lights is a cost effective way to maximize your crime prevention while adding value and diversity to your landscape.  Lighting should be designed for proper photometrics, proper illumination that reduces glare and increases view corridors. Your lighting can provide up-lighting, down-lighting and pathway lighting that is providing sufficient and cost effective lighting throughout your property, detouring offenders.

The kind of shrubs and trees included in your landscape and where they are planted can add to home security as well as beautifying the property and increasing the resale value.  The advantage plants have over architectural elements such as low walls or fences is cost and versatility.  The disadvantage of plants is they require some frequent maintenance and care.  Plantings will contribute to a positive and attractive environment, softening the frigidity and raw elements of urban living, while enriching the spatial qualities of the site.

When addressing a mature landscape, clear and maintain sightlines between street and residential property to allow better visibility from the street or sidewalk.  Trees and low shrubs are perfect for defining an area but you must allow visibility between the shrub and lower branches of the tree canopy.  When utilizing trees to define a project perimeter, small trees are most effective at separating potential conflicts between adjacent use areas and remember these trees must be positioned not to block site surveillance areas.

Stormwater Chain, Capturing Stormwater Run-Off (Final in a Series)

Landscape, Street and Parking Swales

It has been stated and proven the need to create greater environmental awareness in dealing with water conservation is evident. Bringing awareness and understanding will create the means to implement some of these simple principles.  Landscape, street and parking lot swales are threads in the stormwater chain and part of these simple and responsible principles.

Landscape swales temporarily store run-off water while reducing pollutants with its vegetation from small to moderate rain events.  These swales are usually low depressions designed to collect, reduce flow, and move stormwater run-off with its greatest attribute of allowing water to infiltrate into the ground, re-charging ground water while cleaning the water of its pollutants.

These swales, as recommended by The Portland Manual are average 6” deep by 2’ in width in private and commercial use, and a maximum of 4’ wide for public swales.  This is one of the main differences between a swale and a bio-retention pond that may include a forebay area to encourage sedimentation and substantially deeper to accommodate greater amounts of water run-off.

Street swales provide tremendous benefits to residential neighborhoods, not only for reducing run-off and flow rates, but also for integration within streets to slow down traffic by narrowing the street and essentially creating green streets.  These street swales are small scale features designed to take run-off from the street.

Typical parking lots have been designed with raised or curbed greenspaces dividing parking rows.  To take advantage of collecting stormwater, they are now being properly designed with depressed sunken greenspaces that are vegetated within these large scale non-pervious parking areas.  Again, the vegetation is essential to filtering contaminants that may be within the run-off water.  Landscape architects & designers are now looking at ways to actively and aesthetically install these swales alongside domestic driveways and parking areas near gardens and residential yards to continually expand the possibilities of capturing stormwater.

The Stormwater Chain- Green (Living) Roofs

The stormwater chain is comprised of many components that can be put together in various combination's to suit your particular garden or landscape.

The stormwater chain composition includes bioretention facilities, stormwater gardens and rain chains, rills and channels to rainwater harvesting and living roofs.  By utilizing just one of these elements, you can help reduce stress on existing and overwhelmed stormwater drainage systems by breaking the conventional drainage chain of impervious surface (such as roof or pavement) to sewer.

Green roofs, as I will refer to them in this post, are layers of living vegetation installed on tops of buildings or structures.  They manage run-off by reducing run-off flow rates from small to moderate storms and they also provide cooling in the summer months and reduce heat loss in the cooler winter months.

Green roofs are typically referred to as “intensive” or “extensive”.  An extensive green roof is more lightweight designed for shallow root systems like sedum and moss communities and are easier to engineer and retrofit older, thinner roofs.  Intensive green roofs can sustain larger shrubs and small trees and conifers.  Green roofs can be biodiverse and visually pleasing, not monochromatic and boring as was the case in the earlier turf or grass roofs of Scandinavian log cabins.

When you plan your green roof, typically it contains a waterproof layer (membrane), a drainage layer, geotextile filter mat, the substrate (growing medium) and your vegetation referred to as your living elements.  The simplest approach to planting is using smaller sized plugs or already grown tiles that can be supplied by certain garden centers.  These plugs and / or tiles are planted directly into your substrate.

Green roofs are critical in reducing the amount of run-off that reaches our stormwater drainage systems, taking the strain off of older stormwater systems and deteriorating infrastructures in most urban areas.  With roofs representing 40 – 50% of the impermeable surfaces in urban areas, you can see the potential role green roofs can play in reducing run-off.

Next week I will discuss another major component in the stormwater chain- capturing water run-off with landscape swales.