Board of Supervisors Meeting Date:


Planning Commission


May 12, 2005

Staff Lead:



W. Todd Benson, Assistant Zoning Administrator


Community Development



A Zoning Ordinance Text Amendment to Section 2-308.4 to Eliminate Density Credit for Floodplain


Topic Description:


Section 2-308.4 of the Fauquier County Zoning Ordinance allows a fifty percent (50%) density credit for land located within the 100-year floodplain for residential zoning districts.  The proposed amendment eliminates all density credit for floodplain in the residential zoning districts.


Requested Action of the Board of Supervisors:

Conduct a public hearing and consider adoption of the attached Ordinance.

Financial Impact Analysis:

No financial impact analysis has been conducted.


Summary Staff Report:


For many years, the Fauquier County Zoning Ordinance has prohibited development in floodplains and further required homes to be set back an additional 25 feet.  In all but the RA and RC zones, the County also has allowed a developer a 50% density credit transferable to his non-floodplain lands.  At issue, is the 50% credit. The proposed text amendment would eliminate the transferred density credit in all residential zoning districts.


Authority for this action is found in the Virginia Code, which allows localities to regulate density and protect water quality, and further mandates that localities draw their ordinances with an eye toward preventing loss of life and property due to floods.


On August 26, 2004, the Planning Commission voted to initiate the text amendment and schedule a public hearing.  On December 8, 2004, the Planning Commission held a public hearing on the proposed text amendment and unanimously voted to forward the text amendment to the Board of Supervisors with the recommendation that it be adopted. On January 13, 2005, the Board of Supervisors held a public hearing.  With few exceptions, there was wide public support for the proposal. Nevertheless, the Board remanded this matter to the Planning Commission for more investigation and community planning.  On January 27, 2005, the Planning Commission again initiated a text amendment process and scheduled the public hearing for March 31, 2005.    Again, the Planning Commission forwarded it to the Board of Supervisors with a unanimous vote for adoption.


At issue is a reduction of density - a cessation in the transfer of density credits from unbuildable floodplains to adjacent land.  Less density usually means less impervious surface and more vegetated land.  The relationship between vegetated land and water quantity and quality has been known for over 100 years.


In his first Annual Message to Congress, President Theodore Roosevelt observed:


The forests are natural reservoirs. By restraining the streams in flood and replenishing them in drought they make possible the use of water otherwise wasted. They prevent the soil from washing, and so protect the storage reservoirs from filling up with silt. Forest conservation is therefore an essential condition of water conservation.


With increasing scientific sophistication, the value of vegetation – not just trees – on water quantity and quality increasingly is apparent.  Indeed, the Chesapeake Bay Preservation Act, adopted by the Virginia General Assembly in 1988, is based entirely upon the precept that vegetative buffers improve water quality. The Chesapeake Bay Local Assistance Department (hereinafter “Bay Department”) has developed a buffer manual that restates what Roosevelt told the Congress 103 years ago:


The urbanization of a watershed has several effects on the

hydrology of an area. The development of an area alters the natural

drainage pattern as roads and buildings are fit onto the landscape.

This also increases the amount of impervious surface that then

amplifies the quantity of stormwater runoff that is concentrated

before being released into the existing drainage system. In addition

to augmenting the runoff quantity, the concentration of water boosts

the speed at which it travels, multiplying the scouring power in

surface streams and rivers. Additionally, as most of the existing

natural vegetated areas are denuded, local rises in the water table

can stress existing deep-rooted trees.


The rapid transport of water away from the land surface by

stormwater conveyance systems reduces the amount of water that

seeps into the soil and recharges the ground water system….The

recharging of the ground water is important for maintaining wells

and supplying the base flow waters that feed streams.


See also, Correll, D.L., Buffer Zones and Water Quality Protection: General Principles (1997)(“Most of the water flowing down the channel of most streams reached the channel at some point as ground water moving from a recharge area to the stream.”)  As noted on the Virginia Department of Conservation and Recreation’s Stormwater Management Program website: “Pervious surfaces, such as meadows and woodlands, absorb and infiltrate rainfall hence generate little runoff. Urban landscape typically covers such areas with impervious surfaces, such as pavement and rooftops. These impervious surfaces generate runoff every time it rains. (A typical city block generates nine times more runoff than a woodland area of the same size!) The quantity of runoff from these areas quickly overwhelms natural channels and streams, often causing channel erosion, localized flooding and property damage.”

The Virginia Department of Conservation and Recreation has a chart that quantifies the relationship between runoff and impervious surfaces.  It is attached as Attachment 2.  Essentially it shows what happens to ground recharge, evaporation and transpiration, and runoff as the percentage of impervious surfaces increase.  As a general rule, natural groundcover allows 10% runoff.  A 10 to 20% impervious surface allows 20% runoff. With 35% to 50% impervious surface, we see 30% runoff.  Seventy five percent impervious surface yields approximately 55% runoff.


Doug Morgan, Fauquier County Senior Planner,  spent years doing open space calculations for single family housing in Stafford County.  Based upon his experience and training and his knowledge of Fauquier County’s system, he estimates that the average, conventional R-1 house in Fauquier County has a minimum lot size of 40,000 square feet; the total amount of impervious surface based on house, garage, sidewalk, and driveway for the new construction is estimated less than 10% impervious.  He  based this on a calculation of a 2,500 square foot house with a 20’ x 20’ attached garage, 35’sidewalk, a 12’ x 50’ driveway, and a 10’ x 10’ shed on almost an acre lot.  Using the State’s graph, runoff doubles.


If you take the same 40,000 square feet and re-zone it to R4, you then have 4 times the amount of impervious surface on the same amount of land, making the total roughly 40% (37.4%).   Runoff triples.  The downstream riparian owners become the recipients of this trebled runoff.


Culturally accelerated runoff also alters stream patterns both up and downstream of the point/area of entry, resulting in adjustments to the configuration of the stream channel as it seeks balance to accommodate this change.  This will impact existing erosion/deposition patterns with accompanying changes to channel depth, width, and meander patterns.


Plants also have a beneficial impact on water quality. Among other things, they remove nutrients from stormwater.  Nutrient overloading in Virginia streams and rivers, as well as the Chesapeake Bay, is a major problem.


However, absorption is not the only way plants eliminate nutrients.  As noted by the Bay Department:


While an herbaceous buffer can do significant good by

slowing surface runoff and trapping sediment, the most significant

gains for removal of nitrogen come from a mixed forested buffer of

woody plants. The deep roots entering the ground water supply the

necessary carbon and harbor bacteria in the soil for denitrification,

so nitrogen can be permanently removed from the system. Much of

the nitrogen in a system has entered the ground water quite a

distance away from the surface waters. These underground aquifers

then slowly carry the nitrogen and other contaminants to surface

waters. So, even in an urban situation where most of the

stormwater from adjacent properties is piped through a buffer, it still

has an important role in pollutant removal. Woody vegetation in

these buffers can be of significant value in removing ground water

contaminants before they reach surface waters.


Stormwater is also cleansed of sediments, nutrients, and toxics as a result of particulate trapping within vegetated areas.  Correll, D.L., Buffer Zones and Water Quality Protection: General Principles (1997).


Vegetation also retards the speed of rising streams.  By slowing current, sediments, themselves a pollutant, can settle out and become deposited on the floodplain, rather than fouling the water and stream bed.  As noted by the Bay Department, “When suspended sediments settle to the bottom of the channel, critical habitat for fish and other species may be degraded. Benthic organisms can suffocate, depleting the food supply for many fish, and reducing the abundance of filter-feeding organisms that help clean the water. The turbidity also prevents sufficient light from reaching submerged aquatic vegetation (SAV) and benthic algae necessary as food for the various forms of aquatic life.”


For water quality improvement, Fauquier County would ideally have wide vegetated swaths adjacent to rivers and streams to slow and absorb the stormwater and provide an opportunity for percolation into the soil.  As noted in the Chesapeake Bay Local Assistant Department manual on riparian buffers:  “Vegetated riparian buffers are one of the most functionally beneficial and biologically diverse systems….Benefits derived from vegetated riparian buffers, especially forested buffers, include water quality enhancement, stormwater and floodwater management, stream bank and shoreline stabilization, water temperature modification, wildlife habitat protection, and absorption of airborne pollutants. These benefits can translate into increased quality of life and real savings for the community.”


However, one should not become too dogmatic on the definition of buffers.  The Bay Board discusses them because they are part of their regulatory scheme.  However, all vegetated land provides salutary benefits for stormwater quality.  It is their location and size that contributes in varying degrees to efficiency.  As subdivision occurs, the benefits of vegetated lands are lost in piecemeal fashion.  The remaining vegetative land continues its salutary efforts albeit with increased water to slow and more sediments and pollutants to intercept. Alliance for the Chesapeake Bay, Riparian Forest Buffers, Linking Land and Water (July 2004), at 9(“Nevertheless, trees remain vital to urban ecology. …Urban trees help reduce stormwater runoff and encourage infiltration – intercepting falling rain, absorbing and storing water, reducing runoff, protecting soil from erosion, filtering pollutants, and improving air quality.”)


Recognizing that each site is different, the Virginia Department of Conservation nevertheless notes:  “Studies have shown that there is a significant impact on water quality when 19% or more of a watershed is rendered impervious….[T]his is roughly equivalent to one house for every two acres.” DCR, Better Land Use Planning for Coastal Virginia (November 2004).


At present, the Commonwealth of Virginia has a Nutrient and Sediment Reduction Strategy for the Potomac watershed, which a part of Fauquier is in.  “The …strategy…is born of the realization that our actions on the land have a major impact on the waters into which they drain.” Commonwealth of Virginia, Chesapeake Bay Nutrient and Sediment Reduction Tributary Strategy for the Shenandoah and Potomac River Basins (April 2004)(Draft(hereinafter “Strategy”), at 4. The goal is to reduce pollutants from entering the waters of the Commonwealth.  The Strategy calls upon localities to take actions to reduce nonpoint source pollution in their land use decisions.     The proposed text amendment is consistent with this program to improve the Potomac River.


Virginia, Pennsylvania, Maryland, the District of Columbia, and the Federal Government are signatories to the Chesapeake Bay Agreement. Pursuant to the Chesapeake Bay Agreement, the Commonwealth of Virginia has committed to limiting sediments and nutrients into the tributaries of the Bay by 2010.  Elimination of the floodplain credit is also consistent with this commitment by the Commonwealth.


Because the proposed text amendment is authorized by law and consistent with the Commonwealth’s efforts to improve water quality and the Chesapeake Bay, the text amendment is also consistent with Article XI, Section 1 of the Virginia Constitution where it is declared that the “Commonwealth's policy [is] to protect its atmosphere, lands, and waters from pollution, impairment, or destruction, for the benefit, enjoyment, and general welfare of the people of the Commonwealth.”


It is recommended that Section 2-308.4 of the Zoning Ordinance, which addresses density calculations, be revised.  The proposed revision would affect density calculation in all residential districts.   Density calculations in the rural districts (RA and RC) would not change and would continue to have full density credit for land in floodplain.  


The proposed revision is:




            [1-3 same]


4.   In all other zoning district categories, the maximum density shall be calculated on the gross area of the lot except that:


A.  Only fifty (50) percent density allowance shall be calculated on that area of a lot comprised of floodplain, quarries or existing water bodies.


B.   Only thirty (30) percent density allowance shall be calculated on that area of a lot comprised of slopes in excess of twenty-five (25) percent grade.


C.   Only fifty (50) percent density allowance shall be calculated on that area of a lot comprised of slopes in excess of fourteen (14) percent but equal to or less than twenty-five (25) percent grade.


D.  No density allowance shall be calculated for any area of a lot in an existing street right-of-way, floodplain, or quarry.


            [5-7 same]



This ordinance has no impact on allowed uses of land.


This ordinance will not affect a lot which is otherwise buildable today; buildable lots are  grandfathered by § 2-403.


At the Planning Commission’s previous public hearing, the question was raised about the fairness of removing floodplain density in residential districts but not from conservation and agricultural districts; a lack of uniformity was suggested. The uniformity requirement is found in Virginia Code § 15.2-2282 (emphasis added):  “All zoning regulations shall be uniform for each class or kind of buildings and uses throughout each district, but regulations in one district may differ from those in other districts.” For example, there is no requirement in the law for the regulations in Agriculture (RA) or Conservation (RC) zones to be the same as a Residential (R-1) zone.  The RA and RC zones are designed in the Code and Comprehensive Plan to protect open space, agriculture, silviculture, and conservation uses.  There is nothing discriminatory in having one set of regulations for such purposes and another set of regulations for concentrated residential development which is principally in service districts. 


Identify any other Departments, Organizations or Individuals that would be affected by this request:


Department of Community Development

Development Community

Property Owners




1.   Proposed Text Amendment

2.   Impervious Surface Chart