Green street landscape design approach to street stormwater management
May 27, 2012
Green’s stormwater program focuses on designing for stormwater connectivity to natural stormwater resources in the natural environment.
An increasingly common focus of new green street and green urban design practices is stormwater management through strategies designed to manage the hydrologic cycle of stormwater and actively link the built environment to stormwater ecosystems.
The recent US Green Building Council’s (USGBC) Stormwater Design Guide is an excellent example of a resource that is enabling stormwater practitioners to design with consideration for the hydrologic cycle and ecological function of urban stormwater in a natural environment.
In this article, we will explore the green street landscape design approach to stormwater management, by taking a closer look at a recent stormwater management project in the Central Park community of Manhattan, New York. We will also discuss implications for future stormwater projects that are adopting this approach.
Measuring success: What is a green street?
New York’s green streets are a program that is focusing on improving green street landscaping to reduce stormwater runoff. Much of the ongoing interest and research into green street landscaping is happening because of the national interest in addressing water pollution.
In October 2010, the US Green Building Council released the Green Building for Healthy Neighborhoods publication (Hou 2011). This publication provides an overview of the State of Green Streets, a program being coordinated by the New York City Department of Citywide Administrative Services (DCAS) and the US Green Building Council.
The US Green Building Council’s (USGBC) Stormwater Design Guide is another important resource on green stormwater management. Both the State of Green Streets and the Stormwater Design Guide emphasize that stormwater design should be guided by the Natural Capital Implementation Strategy (NHIS) model, which is a framework for integrating the management of natural resources.
The overarching goal of the Green Streets program is to foster the following:
Project leaders from various organizations, including the New York City Department of Transportation (NYCDOT), DCAS, and the City’s Department of Environmental Protection (DEP), conducted the largest Green Streets project in New York City. Over three years (2009-2011), the project was designed and implemented to improve the stormwater performance of a pedestrian street network that was being rebuilt.
Project priorities included an emphasis on reducing impervious areas, eliminating infiltration basins and detention ponds, improving soil health, and connecting stormwater to watercourses.
Part of the NYC Green Streets program
In collaboration with the NYC Department of Design and Construction, many public agencies and private development interests have participated in a stormwater pilot project that will span the 2010-2015 life of the 5th Avenue streetscape.
First Avenue, running north to south, will host the pilot project on the north side of the avenue. The complete north side of the avenue will be redesigned in 2010.
The pilot program will focus on five general areas: 1) Green infrastructure and stormwater management, 2) soil stabilization and drainage enhancements, 3) sediment, 4) erosion, and 5) riparian and other parkland.
Green street landscape design approach to stormwater management
A Green Streets program will never succeed unless it is designed in a holistic fashion that considers the entire hydrologic cycle, soil health, and ecosystem services. In other words, it is not enough for designers to focus on just one or two of these ecosystem services. They must design in a way that addresses all of them.
The NYCDOT partnered with the DEP, DCAS, and the NY Downtown Green Steet Partnership in the development and implementation of this stormwater project. The NYC Green Streets program is a partnership of public agencies (DEP, NYCDOT, DCAS), neighborhood associations, design professionals, and landscape professionals, as well as local development interests and property owners.
During the planning and design phases, stormwater and soil engineers at the NYC DEP and engineers at the DCAS assessed the physical conditions, hydrology, and socio-economics at each site. DCAS provided funding and oversight of construction, and the NYC DEP and DCAS helped develop the plans for implementation of each element of the project.
The NYC DEP’s Stormwater Technical Advisory Group (STAG) played an important role in developing the plans and monitoring the performance of the NYCDOT, NYC DEP, and DCAS throughout the design and implementation phase.
As part of the design, efforts were made to develop a green street for stormwater management, a street for the natural environment, and a neighborhood for the people. The project emphasized improving the quality of life by reconnecting the community to the environment, through the quality of the streetscape and surrounding amenities.
The green street program team defined green streets as roads that reduce runoff and filter sediment. The design emphasizes that natural and biological resources can improve quality of life and reduce the risks associated with stormwater runoff.
For this project, a large part of the design efforts were devoted to increasing the natural capacity of the site to increase its ability to absorb stormwater run-off.
Many stormwater improvements were also focused on improving the quality of life for residents. The project aimed to create a streetscape that will improve the resiliency of the built environment to accommodate climate change. The team made sure that all public facilities would be located out of the flood zone and would be equipped with drainage pipes to reduce flooding hazards.
Design principles were developed based on the stormwater, urban forestry, and ecology principles. The green streets approach is a combination of green infrastructure, green stormwater management, green urban design, and ecological stewardship (Figure 1).
In 2010, the environmental design team applied an ecological approach to stormwater management, which considers the hydrologic cycle of the natural environment (Bungay 2009). It also considers the soil and soil structure as an important ecological system.
The project focused on a neighborhood street approach. The neighborhood street approach is a modification of the traditional street to reduce the amount of impervious surface areas and improve infiltration (UNESCO 2003).