Discussion Points - Expanding the proposed MOD Stream Buffer provisions Countywide



The MOD framework would significantly increase the number of streams within the County that would have stream buffer preservation requirements, and would significantly increase the width of the buffers compared to existing regulations.


Number of Stream Miles Affected

Currently intermittent and perennial streams require a buffer in Water Supply Protection Areas (watersheds draining to drinking water supply reservoirs).  In the remainder of the County only perennial streams require a buffer. 

Total stream miles in the County currently requiring a buffer = approximately1,469 miles


MOD proposal would add requirements for intermittent streams in the remainder of the County.

Total stream miles in the County that would require a buffer with MOD Countywide =approximately 2,197 miles


Ø      Total increase of approximately 728 miles.


Acreage of Land Affected

The buffer width currently required is 100’ on each side of the stream, resulting in a buffer corridor 200’ wide. 

Total acreage of buffer in the County currently required = approximately 35,612 acres


The MOD proposal would double the width of the buffer to 200’ on each side of the stream, resulting in a buffer corridor 400’ wide.

Total acreage of buffer in the County required with MOD Countywide = approximately 106, 521 acres.


Ø      Total increase of approximately 70,909 acres



Buffers perform the functions of improving water quality through pollutant removal (including nutrients nitrogen and phosphorus), filtering out sediment, controlling erosion, providing for flood control, and the creation of habitat for aquatic and terrestrial species.  There is substantial research on how wide a buffer needs to be to optimally perform these functions.  Different widths are necessary for these different functions, so part of the issue is to determine what specific functions we are hoping to achieve from the buffer.


Doubling the width of the buffer from 100’ to 200’ is not likely to yield additional water quality benefits in terms of pollutant and nutrient removal.  Research shows that a forested buffer 100’ wide performs very well at improving water quality and at improving aquatic habitat.  Additional width does not appear to contribute to a proportional increase in the ability of the buffer to perform these specific functions. 


However, adding width is very likely to yield benefits for wildlife habitat for terrestrial species and could provide better storage for floodwaters.  Research indicates that buffers as wide as 300’ are desirable to achieve optimal habitat.  If the County’s buffer width were doubled and resulted in a 400’ wide corridor, a proportional improvement in habitat could be expected.  In addition, research indicates that to provide maximum protection from floods and maximum storage of floodwaters, a buffer should include the entire floodplain.  The County’s current buffer requirements do include the floodplain, except in the Development Areas.  Extending the buffer to 200’ would likely incorporate more floodplain and provide improved protection from flooding in these more densely developed parts of the County.



Current stream buffer requirements are contained in the County’s Water Protection Ordinance.  Sections 17-317 through 17-322 would need to be amended to incorporate the changes.  The enabling authority to change these buffer requirements exists, under the Chesapeake Bay Preservation Act, from which our current requirements are taken.  Staff time would need to be devoted to the task of amending the ordinance.


Currently staff is able to administratively authorize ‘variances’ to the buffer requirements for items such as driveways and roadways through a buffer to allow access for reasonable use.  The MOD changes include a provision that a special use permit would be needed to authorize such variances.  This would substantially increase the amount of staff time and effort to coordinate these requests from applicants, and would significantly increase review and approval time.  However, the MOD changes could result in fewer applicant requests to encroach into the buffer, resulting in higher quality buffers throughout the County.


These changes would require additional field work for applicant and staff to field delineate intermittent streams that do not appear on the USGS maps.  This task is currently only performed in the Water Supply Protection Areas.  It is very likely that requests from applicants to field delineate intermittent streams in the remainder of the County would substantially increase.


These changes would require additional effort during staff’s plan review to ensure that buffers are delineated and preserved on development proposals.  In addition, the changes would require additional staff inspection and enforcement of buffer area protection during construction.  


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