If the landowner is required to submit a plan to preserve or establish a vegetative buffer under sections 12.09.020 or 12.39.110., Vegetation Preservation, or, if vegetation has been removed in violation of 12.09.020, requirements, the preservation plan or violation must be created and mitigated per the following:
(a) Mitigation Methods. There are basically four (4) methods of mitigation that will establish or maintain a buffer. Each method involves preserving or establishing three vegetative layers: ground cover (grasses, etc.), shrub understory, and tree canopy. Attempts should be made to duplicate or mimic the undisturbed vegetative habitat that exists around the particular water body.
1. Avoidance. Some of the buffer may be totally intact or undisturbed. If that is the case, that area does not have to be mitigated. However, the affidavit shall state that the landowner will not disturb the area and will remain compliant with placement of the viewing corridor, etc.
2. Natural Recovery. Some of the buffer may be present, but some of the understory vegetation may have been removed, or the area may have been mowed down to the edge of the water. The goal is to reestablish the natural condition, had the area not been disturbed. The recovery method involves simply stopping all mowing or clearing and letting the area regenerate naturally. It is important to note that in some cases over seeding with native plant species may help facilitate establishment of the natural condition.
3. Accelerated Enhancement Recovery. This method is similar to natural recovery, but entails actually installing some plant materials to achieve proper vegetation density, as outlined in Density, below. Simply, the landowner fills in areas that are too thin or where the vegetation is missing.
4. Accelerated Creation Recovery. This method is used when no buffer exists. The area in question may have been graded to bare soil or the site may have been mowed for many years. Creation will involve planting groundcover, shrubs and trees based on the Table of Density Requirements below.
(b) Density. If you have to install plantings, a specific vegetation density is required. Refer to the Table of Density Requirements below, which denotes how many plantings should be installed per square foot per vegetative layer (groundcover, shrub or tree canopy). Planting dates should be verified with the chosen plant supplier. The landowner may take credit for existing plants. (For example, if all soil is covered by grasses, the landowner does not have to install plantings in that layer. Likewise, if the buffer has 10 existing trees, the trees would count as 3 new trees.)
LAYER | MAX. NO. OF DIFFERENT SPECIES | NO. TO BE INSTALLED PER 100 SQ. FT. | CREDITS FOR EXISTING VEGETATION | PLANTING DATES |
|---|---|---|---|---|
Tree Canopy | 3 | 1 | 1 existing tree = 0.3 new trees | 4/15—11/15 |
Shrub Understory | 4 | 2 | 1 existing shrub = 0.5 new shrubs | 4/15—11/15 |
Groundcover Plant (bareroot/rootstock/potted) Plugs | 1 | 70 | n/a | 5/15—11/15 |
Groundcover Seedlings, Warm and Cool Season Grasses (More diverse seed mixes are ideal) | 1 | General seed broadcasting | Complete cover of bare soil | 5/1—9/15 |
(c) Plant Selection. When selecting the plantings to install, the landowner shall use species, which are native to the region and nonnoxious. The landowner should pay special attention to existing native species growing onsite as well as soil type, soil moisture, and sun exposure conditions specific to the subject property. When selecting groundcover, a diverse seed mix is highly recommended to maximize chances of successful establishment and promote greater species diversity.
(d) Erosion Control and Maintenance. As with any construction project, erosion control measures should be utilized during mitigation. Runoff from impervious structures should be diverted away from the water, and, matting or mulch should be used as groundcover plantings are taking root. The mitigated area is intended to be a natural area so little maintenance is needed. There should be no need to rake or fertilize, and selective mowing should only be conducted to control brush and manage noxious species encroachment. For detailed information on care, maintenance and weed management of the mitigated area the landowner is encouraged to consult the UW-Extension, Conservation Specialist, Botanist, or Environmental Consultant.