BMP Field Manual
Chapter 5 - Riparian Management Zones
- Background: What is a RMZ?
- Agricultural and Urban Areas
- Definitions
- Existing Regulations
- Best Management Practices for Riparian Management Zones
Riparian management zones (RMZs) are land and vegetation areas next to lakes and streams where management practices are modified to protect water quality, fish and other aquatic resources. These areas are complex ecosystems that provide food, habitat and movement corridors for both aquatic (water) and terrestrial (land) communities. Also, because these areas are next to water, RMZs help minimize nonpoint source pollution impacts to surface waters.
Riparian management zones help to:
- Filter sediment and nutrients from runoff. As runoff water moves through plants and the duff layer (needles, leaves and decaying matter), it slows and drops sediment that has been carried along. This settling process keeps sediment and nutrients from flowing into streams and lakes. It also allows plant roots to take up the nutrients that have dissolved in the runoff and soaked into the soil, further reducing the amount of pollution flowing into lakes and streams.
- Allow water to soak into the ground. Trees and plants, leaves and twigs slow surface runoff, allowing the water to soak into the soil. This helps to reduce peakflow levels in streams and replenishes the groundwater that helps maintain lake levels and stream flows.
- Stabilize streambanks and lakeshores. Trees and plants along streambanks and lakeshores can reduce soil erosion because their roots hold the soil together, making it more difficult for waves, currents and runoff to wash the soil away. Plants also reduce the impact of raindrops on exposed soil, decreasing erosion.
- Shade streams. In most cases, plants and trees along streambanks are necessary to shade streams, keeping the water from becoming too warm for aquatic life in the summer.
- Provide food and habitat for aquatic organisms. Fallen leaves and other organic debris from trees are the base of the food chain for aquatic organisms in small forest streams. Large woody debris (large fallen logs, generally at least 12 inches in diameter with an anchored root ball) create riffle areas and plunge pools, critical habitat for fish and other aquatic organisms. The pools trap leaves and twigs long enough for microorganisms to decompose them. These microorganisms become food for insects and other invertebrates, which in turn become food for fish.
Riparian zones are as valuable in agricultural and urban areas as they are in forested areas. Runoff from cultivated fields, as well as city streets and lawns, can contain sediment, pesticides and fertilizer. Plants in riparian zones can filter out these contaminants, reducing the amount of pollutants entering waterbodies.
Riparian zone landowners in all agricultural and urban areas should maintain or restore riparian management zones. Do not allow livestock to graze in forested RMZs. (Contact the USDA Natural Resources and Conservation Service or your local land conservation department to establish a grazing plan).
Lake - A still waterbody that:
- is navigable
- has an ordinary high-water mark
- has a bed that indicates "reasonably permanent" surface water.
Stream - A watercourse that:
- has an ordinary high-water mark
- has bed and banks
- flows at least periodically
- has an easily identifiable beginning and end
- does not lose its character as a watercourse even though it may break up and disappear temporarily and reappear downstream.
There are two kinds of streams:
- Perennial streams flow throughout most (i.e. >50%) of the year.
- Intermittent streams usually flow only after rainstorms or snowmelt and are, therefore, dry most of the year. Intermittent streams must be protected because they channel runoff into perennial streams and lakes and may become part of the aquatic ecosystem when water flows in them.
The ordinary high-water mark is the point on the bank or shore up to which the presence and action of the water is so continuous as to leave a distinct mark either by erosion, destruction of terrestrial (land) vegetation, or other easily recognized characteristic.
Stream and Lake high-water marks.
A waterway is navigable if it has bed and banks, and it is possible to float a canoe or other small craft in the waterway on a regular reoccurring basis - even if only during spring runoff.
Note: Lakes and streams (perennial and intermittent) identified on current USGS topographical maps (7.5 minute/1:24,000 scale), should be considered navigable. Other lakes and streams may be determined to be navigable by a Wisconsin DNR water management specialist. If you have a question about navigability, contact a Wisconsin DNR water management specialist.
All cutting practices next to lakes and navigable streams must be consistent with local county shoreland and wetland zoning ordinances. Wisconsin Administrative code, NR 115, provides state-required minimum standards for the cutting of trees and shrubbery to be included in county shoreland ordinances to protect the natural beauty, control erosion and reduce the flow of effluents, sediments and nutrients from the shoreland area. A special exception (or conditional use) permit may be required to harvest next to lakes and navigable streams. When planning to harvest within the RMZ, contact your local county zoning office before beginning any harvesting. For more information about Administrative Code NR 115, see Regulations.
Stream crossings, grading next to lakes and streams, and other forestry activities are also subject to permits as described Permits, and other regulations, as described in Regulations. Contact a Wisconsin DNR water management specialist for more information.
Best Management Practices for Riparian Management Zones
There are three categories of Riparian Management zones for BMPs:
- Lakes and navigable perennial streams;
- Navigable intermittent streams; and
- Non-navigable streams.
BMPs Common to All Three RMZ Categories
- Locate roads outside the RMZ unless necessary for stream crossings. For stream crossings, follow recommendations in the Stream Crossings section of Forest Roads.
- Locate landings outside the RMZ.
- Do not move slash into or pile slash within the RMZ. Keep slash out of lakes and stream channels and away from areas where it may be swept into the water.
- Minimize soil exposure and compaction to protect ground vegetation and the duff layer.
Note: On steep slopes or on areas of highly erodible soils, you should widen the RMZ.
The three riparian management zones.
- BMPs for Lakes and Navigable Perennial Streams
- Do not operate wheeled or tracked harvesting equipment within 50 feet of the ordinary high-water mark except on roads or at stream crossings.
- Use selective harvesting and promote long-lived tree species appropriate to the site. Long-lived tree species include: (1) hardwoods such as sugar and red maple, white and black ash, elms, and oaks; and (2) conifers such as eastern hemlock, white pine, red pine, and white cedar.
- Harvesting intervals should be a minimum of 10 years.
- Harvesting plans should leave at least 60 square feet of basal area per acre in trees 5 inches DBH (diameter breast height) and larger, evenly distributed.
- Develop trees 12 inches DBH and larger.
- BMPs for Lakes and Navigable Intermittent Streams
- Operate wheeled or tracked harvesting equipment within 15 feet of the ordinary high-water mark only when the ground is frozen or dry.
- Use selective harvesting and promote long-lived tree species appropriate to the site. Long-lived species include: (1) hardwoods such as sugar and red maple, white and black ash, elms and oaks; and (2) conifers such as eastern hemlock, white pine, red pine, and white cedar.
- Harvesting intervals should be a minimum of 10 years.
- Harvesting plans should leave at least 60 square feet of basal area per acre in trees 5 inches DBH and larger, evenly distributed.
- BMPs for Lakes and Non-Navigable Streams
- Operate wheeled or tracked harvesting equipment within 15 feet of the ordinary high-water mark only when the ground is frozen or dry.
The RMZ for these waters is a strip of land running along the shoreline of lakes and on each side of streams. It begins at the ordinary high-water mark and extends a minimum of 100 feet landward.
The RMZ for these streams is a strip of land on each side of the stream, beginning at the ordinary high-water mark and extending a minimum of 35 feet landward.
Non-navigable streams are found in the field but may not be identified on current U.S. Geological Survey topographical maps (7.5 minute/1:24,000 scale).
The RMZ for these streams is a strip of land on each side of the stream, beginning at the ordinary high-water mark and extending a minimum of 35 feet landward.
RSS