Low Impact Development Manual for Michigan - OSEH - University ...

• Limit clearing and grading of forests and native
vegetation at a site to the minimum amount
needed to build lots, allow access, and provide fire
protection.
• Promote riparian buffer areas as part of stormwater
management planning.
Source: Planning for Green River Corridors, Oakland
County Planning & Economic Development Services.
Wide buffer maintained during residential construction
Source: Huron River Watershed Council
Stormwater Functions and
Calculations
Any portion of a site that can be maintained in its
presettlement state by using this BMP will not contribute
increased stormwater runoff and will reduce the
amount of treatment necessary. Calculation methodology
to account for this BMP is provided in Chapter 9.
Volume
Protected riparian buffers are not to be included in the
disturbed stormwater management area when calculating
runoff volume (Chapter 9 and Worksheet 3).
Any portion of a riparian buffer area that is mitigated
or revegetated/reforested should be included in the
disturbed stormwater management area, but may be
granted credit in accordance with the applicable BMP
for native revegetation, soil restoration, minimize soil
compaction, riparian buffer restoration, or minimize
total disturbed area.
Peak rate
Runoff from the riparian buffers may be excluded from
peak rate calculations for rate control, provided that
runoff from the riparian buffers is not conveyed to and/
or through stormwater management control structures.
If necessary, runoff from riparian buffers should be
directed around BMPs and stormwater pipes and inlets
by means of vegetated swales or low berms that direct
flow to natural drainageways.
Water quality improvement
Water quality is benefited substantially by avoiding
negative impacts which otherwise would have resulted
from impacts to riparian buffers (e.g., loss of water
quality functions from riparian buffers, from wetland
reduction, etc.).
Cost
The costs of protecting riparian areas relate to a reduction
in land available for development. However, most
riparian areas are located in wetlands or floodplains,
restricting the amount of buildable area.
LID Manual for Michigan – Chapter 6 Page 94