Irving's Grow Zone Program
The City of Irving has created a Grow Zone Program where it provides focus to city owned properties in an effort to positively impact the environment. A “Grow Zone” is an area where mowing is restricted and vegetation is allowed to grow.
Grow Zones help to improve the quality of our soil, water, and air, and also provide helps to provide habitat structure for native and migrating wildlife. Ideally, Grow Zones should contain native and diverse vegetation, which helps to maximize ecosystem services provided by these spaces, and improve overall biodiversity.
Currently, Irving targets city-owned drainage swales and areas along streams as viable places for these Grow Zones.
Visit our Stormwater Interactive Mapping page to view current Grow Zones in the City of Irving.
Types of Grow Zones
Bioswales : are vegetated zones that rest within low-lying areas and that have water channeled through them.
Bioswales are a type of green infrastructure, or blue green infrastructure - as the concept has developed - and are designed to manage water quality and quantity in a watershed. Blue green infrastructure adopts a nature based solution to better help build more resilient communities, expand ecosystem services, and promote biodiversity.
The city chose existing drainage swales as viable locations for creating these bioswales. Historically, these swales were mowed and had aggressive turf grasses growing in them. In some areas, such as Running Bear Park, the undesirable grasses and other vegetation are removed from the site, and the area is seeded for native vegetation: wildflowers, prairie bunch grasses and other native plants. The soil is also prepped in these areas, where soil is transplanted from local riparian and prairie habitats in an effort to inoculate the new area with beneficial microbes, and transplant existing native seed banks from those habitats. The idea takes an ecosystem restoration approach, where we try to restore the ecosystem back to how it previously was before settlement and development occurred. This approach reduces maintenance requirements, and improves the environment in numerous ways.
Sensitive Streamside Areas : are a type of Aquatic habitat found alongside streams that have been left natural with existing and or native seeded vegetation, and that have restricted maintenance activity.
Sensitive Streamside Areas are one example of an environmentally sensitive area, and can also be understood and described as a protected riparian habitat or buffer. Often these areas have been developed over and right up to; when this happens, erosional evens are more likely to occur, as well as flood events and water pollution...not to mention habitat destruction that impacts wildlife. When riparian buffers are maintained, they can often have turf grass present, and that is put on a regular mowing schedule. Not only is this approach labor intensive and harmful for air quality, but it offers little biodiversity and limits potential ecosystem services provided.
More Info & Benefits of this habitat
From an ecosystem perspective, areas that exist along the edges of any aquatic habitat are referred to as riparian habitat. Riparian buffers are important habitat corridors for wildlife and act as a natural buffer from pollution. It’s helpful to think of these areas as sponges that help to soak up and sequester any potential pollutants that pass through them. Microbial life in the soil helps to cycle nutrients and breakdown many of these pollutants, allowing for uptake by plants, and cycling back into the atmosphere.
Maintaining Riparian buffers are helpful for many reasons, including preventing erosion, as the roots of the plants - especially native grasses - help to bind and stabilize the soil in place. This same action of the plants roots also helps to encourage infiltration of stormwater into the ground. As is the case with bioswales - or any habitat with diverse and robust vegetation that is left to grow natural, air quality is improved through reduction of CO2 and air pollutants from the atmosphere, and cooling of ambient and surface temperatures.
The city looks for areas alongside stream corridors that have existing turf grasses present, and or erosion concerns. These areas already have preserved buffers from developments, and so are prime for instituting as a Sensitive Streamside Area.
BENEFITS OF GROW ZONES
BENEFITING SOIL AND WATER
This process of water being channeled through a vegetated area allows for it to be treated through the media of soil, and the decomposers that live in the soil that breakdown many of the pollutants that enter the system. Plant are also called phytoremediators, because they can sequester and remove pollutants from the environment. With the process of water moving through natural vegetated areas, water is also slowed down, and the amount and speed of this water that is eventually discharged into nearby aquatic habitats is reduced, reducing flood risks and erosion.
Wildlife (which include plants and animals) benefit from these habitats as well, as plant growth is essential habitat structure for animals. Native plants are best for benefiting animals, as the existing animals that live locally have evolved with the native plants here over millennia, providing balanced ecosystems that are self-sustaining, and that provide complex or "biodiverse" food webs.
For wild animals, Sensitive Streamside Areas (Riparian Habitats), function as an important corridor for travel and food resources, and offer shelter and breeding habitat. Also by improving water quality, they help benefit the health of a stream, and therefore the chances for species diversity and abundance.
Since mowing at these areas is reduced, so too are the CO2 emissions that would come from mow events. Surface temperatures are reduced due to how plants absorb the suns heat differently (surface albedo), and allow for slow release of it into the environment. Plants also help to reduce ambient air temperatures through transpiration and evaporation (combined called evapotranspiration), which puts moisture back into the atmosphere. Plants also help to improve air quality by removing pollutants from the atmosphere. They do this through two ways: acting as dust collectors, where above ground plant mass captures air pollutants on the surface of the plant, and then also by sequestering pollutants out of the air and into their actual plant parts, such as leaves.
CULTURAL & Economic
These spaces allow for recreational opportunities, including education, research, and environmental observation. When thinking about recreation, such as fishing or hunting, riparian areas and blue green infrastructure such as bioswales help clean water before it enters into our waterways, thus improving the health of the fish or water birds that depend on this water.
From a cultural perspective, we also owe it to our local community to be good stewards of our environment, and make efforts to reduce, and ameliorate pollution, as well as flood risks, and to help preserve the local wildlife community that plays an essential role in our food web. Having these systems in place helps provide ecosystem services that impact our daily lives.
Economically vegetation, especially trees and forest canopy habitat provide economic benefits including reduction of cooling costs in buildings due to shade, and cooling off of ambient temperatures in the atmosphere. For more information on this, refer to this Texas A&M Extension Service page linked here.