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DCR - Virginia Department of Conservation and Recreation
STORMWATER MANAGEMENT
Perennial Stream Determinations

Section 9 VAC 10-20-105 of the Chesapeake Bay Preservation Area Designation and Regulations requires that local governments, as part of their plan-of-development review process or during their review of a Water Quality Impact Assessment ensure or confirm that (i) a reliable, site-specific evaluation is conducted to determine whether water bodies on or adjacent to the development site have perennial flow, and (ii) RPA boundaries are adjusted, as necessary, on the site, based on this evaluation of the site. Local governments may accomplish this by either conducting the site evaluations themselves or requiring the person applying to use or develop the site to conduct the evaluation and submit the required information for review.

intermittent streamThe Chesapeake Bay Local Assistance Board (CBLAB) recognizes that there are a number of approaches to making evaluations of stream perenniality and will not mandate that any particular method be used exclusively. CBLAB has prepared guidance for making distinctions between intermittent and perennial streams. This guidance includes an in-the-field protocol, which will be based largely upon a preponderance of field evidence emphasizing the physical and biological characteristics of the stream channel. CBLAB has reviewed and found three field indicator protocols, field tested in Fairfax County, Virginia, the State of North Carolina and James City County (including some surrounding upper Coastal Plain localities) to be acceptable for making site-specific determinations. Downloadable copies of these protocols and field evaluation forms are listed below:

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The preferred time for making determinations as to whether a stream contains perennial flow is during the height of the local dry season, which in Virginia is usually between July and early September when normal weather conditions prevail. Thus, if the stream contains water at that time, it will likely contain water at all other times of the year. When it is not possible to survey streams in the dry season, additional corroborative evidence is often necessary. Current weather conditions should be noted since recent or overabuntant rainfall can bias any decision. Preferably stream flow observations should not be within 48 hours after the last rainfall. In turn, drought conditions may cause perennial streams to temporarily run dry with water only standing in pools.

Climate Data: Knowledge of recent precipitation and seasonal climatic conditions is very important in corroborating information collected during field evaluations. The following are links to web sites for current and historic climatic data. Many daily newspapers also provide recent climatic data as well as seasonal information (i.e., month-to-date and year-to-date precipitation).

The National Weather Service in Wakefield, Va., includes current and historic data for Richmond, Norfolk, Salisbury, Md., and Elizabeth City, N.C. Navigate to climate/local data to obtain daily, monthly and historical data. Monthly regional data is also available for a number of other areas in the state at this same web site.
http://mi.nws.noaa.gov/climate/index.php?wfo=akq

Precipitation information can also be obtained from the National Weather Service Office in Sterling, VA provides weather recent and historic data for northern Virginia areas from the following web site:
http://www.weather.gov/climate/index.php?wfo=lwx

National Climatic Data Center Web Site may have a fee involved for accessing/obtaining data (may be free for some governmental entities)
http://lwf.ncdc.noaa.gov/oa/ncdc.html

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