A degraded riparian zone is often entirely mowed, which results in bare soil along a stream bank. A lack of vegetation is a visible and primary variable that relates to overall riparian health. A degraded riparian area does not provide the important functions and services of a healthy riparian zone (see riparian function FAQ).
A heavily mowed, channelized creek exhibiting degraded riparian health.
Probably the most important driver of degradation to a riparian zone is the alteration of the natural hydrologic cycle that occurs from the urbanization of a watershed. This change or degradation in rain infiltration, flashy flows and baseflow essentially disconnects the banks and buffers from the stream and the water table. The types of vegetation that thrive in wet, active floodplains cannot survive in this disconnected state and the result is a degraded, abandoned, or upland vegetative community.
Changes that occur to riparian hydrology through urbanization (from Groffman et al. 2003. Down by the riverside: Urban riparian ecology. Frontiers in Ecology and Environment 6:315-321.)
After hydrology, the next most important factor that degrades riparian areas is alteration of the mature vegetative communities that evolve in these areas. This occurs primarily via human intervention, i.e. mowing, agriculture, logging or development. These activities remove the original vegetation, and degrade and compact the soil. These activities, when repeated over decades, make it very difficult to “replant” a healthy riparian vegetative community. Removing the disturbance that is keeping the riparian area in a degraded state is the most important thing to do in riparian restoration.
A trail area in a park where soil is compacted and vegetation is excluded.
A “Grow Zone” is an effort to halt mowing along streams and allow the growth of more dense, diverse riparian vegetation. This improves water quality, lessens erosion, increases wildlife habitat, and provides other ecosystem services. It is our hope that Austinites will embrace these changes and appreciate the benefits of natural stream corridors. If you or your group is interested in getting involved please check out the options under the FAQ “What can I do?”
Adopt-a-Creek groups who have an adopted creek section that’s a Grow Zone are encouraged to monitor the area. They select a 300-foot stream segment that best represents the area and conduct annual monitoring of the same sample plots over time. Monitoring takes place within the same month every year to capture long-term restoration progress. Click here to download the Citizen Riparian Monitoring Protocol.
Riparian zones can support plants that are unable to exist anywhere else. These plants in turn help to keep the riparian zone healthy and functioning properly. A plant guide for creekside residents can be found at Grow Green’s Creekside Homeowners Landscape Design Template , for a more general streamside restoration plant list check the Riparian Template. It is important to remember that healthy riparian vegetation can look shaggy and overgrown as it transitions into a mature woodland.
Download our Wetland Plants Field Guide (Web Friendly 7.8MB - High Resolution for printing 238.4MB) to learn more about plants seen in Central Texas creeks and wetlands.
Click here to download this restoration technique’s management guide for volunteer leaders
Click here to download this restoration technique's management guide for volunteer leaders.
Seed balls are marble sized mixtures of compost, clay, native seeds, and water. They are a cost effective, low maintenance method of re-vegetation which requires little water. Seed balls are scattered directly onto ground and not planted.
- Thoroughly mix dry clay (3 parts), compost (2 parts), and seed mix (1 part) specific for the light/moisture conditions of the site.
- Sprinkle with water until mixture sticks/binds together like cookie dough.
- Take a pinch of the finished mixture and roll (in the palm of your hand) into marble-sized round balls
- ‘throw’ or spread the seed balls within the Grow Zone or add them by coir logs
Maintenance Schedule (for local groups training by WPD in self-led restoration techniques)
Volunteer info
Profile, age range - appropriate for 5+ years old, with adult supervision
Clothes and safety - closed toed shoes.
Provided by Watershed Protection Department for official Grow Zones: Seed Mixes, clay, compost
Ecosystem function can be defined as all of the processes necessary to preserve and create goods or services valued by humans. Healthy functioning riparian zones:
- Improves the natural and beneficial functions of the floodplain
- Prevents stream bank erosion
- Filters storm runoff, removing pollutants before they reach the creek
- Provides habitat and food for a diverse group of animals
- Provides shade that cools air and water temperatures
- Creates a greenbelt forest with diverse tree and plant communities for outdoor enthusiasts
- Reduces the City’s carbon footprint
Riparian zone restoration attempts to restore the natural process necessary to maintain a high level of ecosystem function. In general, the larger the riparian buffer the more ecosystem functions it can provide.
This image shows the various buffer widths associated with riparian zone function. Organic inputs into the stream are important sources of nutrients and habitat (width 15-25 ft). Stream stabilization is maintained by riparian vegetation (width 30-60 ft). Water quality is the ability of the vegetation to intercept runoff, retain sediments, remove pollutants, and promote groundwater recharge (width 20-100 ft). Flood control is the ability for the floodplain to intercept water and reduce peak flows (width 60- 500 ft). Riparian habitat is the ability of the buffer to support diverse vegetation and provide food and shelter for riparian and aquatic wildlife (width 100-1500 ft).
RIPARIAN ZONE RESTORATION METHODS
There are three generalized approaches to restoring a disturbed riparian environment:
(1) rely completely on passive (spontaneous succession)
(2) exclusively adopt active, technical measures
(3) or a combination of both passive and active techniques toward a target goal (Hobbs and Prach 2008). Passively restored sites exhibit robust biota better adapted to site conditions with increased natural value and wildlife habitat than do actively restored sites (Hobbs and Prach 2008).
Passive restoration requires minimal management and is more cost effective than alternative methods. However, passive restoration is often the slower approach and is more dependent on adjacent site conditions. When relying on spontaneous succession the vegetation community of adjacent sites, an approximate 100 meter distance from the disturbed site, is critical for successful restoration (Hobbs and Prach 2008). In general, passive restoration that relies on spontaneous succession should be employed when environmental disturbance is not very extreme (Figure 1) and no negative results (erosion, water contamination, negative aesthetic perception, etc…) are foreseen (Hobbs and Prach 2008). When site productivity and stress are extremely high or low, active (technical reclamation) may be necessary (Figure 1). The persistence of undesirable functional states is an indication that the system may be stuck and will require active intervention to move it to a more desirable state (Hobbs and Prach 2008). Understanding when passive versus active restoration approaches are warranted can increase chances of success and reduced project costs.
Passively restored sites exhibit robust biota better adapted to site conditions with increased natural value and wildlife habitat than do actively restored sites (Hobbs and Prach 2008). Passive restoration requires minimal management and is more cost effective than alternative methods. However, passive restoration is often the slower approach and is more dependent on adjacent site conditions. When relying on spontaneous succession the vegetation community of adjacent sites, an approximate 100 meter distance from the disturbed site, is critical for successful restoration (Hobbs and Prach 2008). In general, passive restoration that relies on spontaneous succession should be employed when environmental disturbance is not very extreme (Figure 1) and no negative results (erosion, water contamination, negative aesthetic perception, etc…) are foreseen (Hobbs and Prach 2008). When site productivity and stress are extremely high or low, active (technical reclamation) may be necessary (Figure 1). The persistence of undesirable functional states is an indication that the system may be stuck and will require active intervention to move it to a more desirable state (Hobbs and Prach 2008). Understanding when passive versus active restoration approaches are warranted can increase chances of success and reduced project costs.
