Ocracoke Island; Photo by Stephen Chandler


The Watershed Management Planning Guidebook provides detailed guidance on how a community can replicate natural surface water hydrology to improve water quality by determining the stormwater runoff volume of a watershed in various land use scenarios and utilizing Best Management Practices (BMPs) techniques, specifically Low Impact Development (LID), to reduce the total volume of runoff. Stormwater runoff serves as a transport for pollutants, such as bacteria, nutrients, chemical and physical pollution. Rather than focusing on reducing sources of contamination or attempting to treat and remove bacteria and other pollutants from stormwater runoff, the management techniques used in this guidebook focus on reducing the overall volume of stormwater runoff in order to limit the conveyance from the land into coastal waters. This guidebook is intended to serve as a framework for local governments and coastal communities to develop coastal watershed management plans that will better position them to qualify for funding. This guidebook utilizes simple geographic information systems (GIS) techniques and the Watershed EZ Tool and Runoff Reduction Scenario Tool to quantify the stormwater volume reduction goal of a watershed.

Guidebook Objectives

A watershed management plan is used to protect and restore water quality.  This guidebook provides detailed instruction for coastal watershed managers to devise a management plan that will:

  1. Establish long-term goals for improving or protecting coastal waters and subwatersheds;
  2. Develop strategies to accomplish these goals;
  3. Ensure stakeholder participation;
  4. Identify and analyze pollutant characteristics;
  5. Measure water quality goals; and
  6. Result in management measures to meet the desired objectives.

How to Use Your Plan in Lieu of a TMDL

When surface waters no longer comply with assigned water quality classifications and standards, the federal Clean Water Act (CWA) mandates that steps be taken to remove the water quality impairment and restore water quality to acceptable levels. This normally involves conducting a Total Maximum Daily Load (TMDL) study to determine how much pollutant loads should be reduced to restore water quality.  Once the study is complete, then a watershed restoration plan is devised to accomplish the desired reductions in pollutant loads.

TMDL studies typically cost many thousands of dollars and can take several years to complete.   For many coastal subwatersheds where pollution is caused by stormwater runoff and not discharges of industrial or domestic wastewater, scientific monitoring has shown repeatedly that altered watershed hydrology creates additional surface runoff that then washes bacteria into downstream coastal waters.  This methodology allows managers to estimate how much additional surface runoff has been created as a result of hydrologic modifications, and establishes a numerical goal for how much runoff must be reduced to restore impaired water quality.  This numerical volume reduction goal, which forms the basis for a watershed management plan, can serve in lieu of preparing a TMDL where there are ample water quality monitoring data and documentation of the relationships among: intensity of land uses, greater hydrologic modifications, and increasing bacteria levels.

The TMDLs and watershed management plans for the Lockwoods Folly and White Oak Rivers were approved by EPA and N.C. Department of Environment and Natural Resources (DENR).  These plans provided guidance for the City of Wilmington to follow in developing the Bradley and Hewletts Creeks Watershed Management Plan, which was approved by the DENR to serve in lieu of a mandatory TMDL. This voluntary plan gives the city time to accomplish restoration efforts without facing a legal mandate from EPA.  This guidebook provides step-by-step instructions for how to devise volume-based TMDLs and/or a watershed management plan.  The methods outlined can be used to satisfy mandatory requirements in coastal watersheds for a TMDL, or to devise a watershed management plan that will serve as a voluntary effort to address water quality impairments.

Other Uses of this Guidebook

In areas where a TMDL assessment has already been completed or will be performed, a watershed management plan can complement restoration efforts. A watershed management plan can present strategies to control non-point source pollution that is not readily addressed through the TMDL process.

Plans developed according to this guidebook can also be effective in improving water quality in areas that are not considered legally impaired.  These are areas where one or more uses for the water (e.g., shellfish or swimming) did not exist when the Antidegradation Policy pursuant to the federal Clean Water Act was established in 1975 (see Chapter 2).  If waters are not legally impaired, there may be no state or federal requirements to improve water quality.  However, a community may want to establish or regain uses of these waters and may do so by constructing a plan according to the guidance provided herein.

How this Guide Compares to the EPA Watershed Handbook

Many elements of this guidebook were adapted from the EPA Handbook for Developing Watershed Plans to Restore and Protect Our Water.  Similarities and differences include:

  1. This guidebook concentrates specifically on coastal subwatersheds with swimming and shellfish water quality impairments.

This allows implementation of management strategies tailored to the differing land use patterns and natural hydrology of coastal area. By having a small project scope, in many cases even smaller than the 12-digit Hydrologic Unit Code (HUC) subwatersheds, planning efforts can become more focused and more easily implemented.

  1.  Instead of attempting to eliminate sources of bacteria, the methods in this guidebook seek to reduce the transport of bacteria by reducing the volume of surface runoff.

Previous projects that tested these methods, including those on the White Oak River, Lockwood Folly River, andHewletts and Bradley Creeks, show that one of the best ways to restore coastal water quality is to mimic natural hydrology and to reduce the overall rate and volume of stormwater runoff. This technique reduces the overall pollutant loads deposited into watersheds. This guide helps set volume reduction goals and develop management strategies for meeting those goals in order to improve water quality. This is effective because impairment of waters is predominantly due to the alteration of hydrology within these very small watersheds.

  1. Following the methodology outlined in this guidebook will ensure your plan incorporates all nine elements of a watershed management plan as required by EPA as necessary to qualify for 319 funding that is used to restore impaired waters.

Incorporation of these nine elements will increase the likelihood that your plan can serve in lieu of a TMDL.  The EPA’s nine minimum elements will be discussed frequently throughout this guidebook, and include:

  1. Identification of causes of impairment and pollutant sources or groups of similar sources that need to be controlled to achieve needed load reductions, and any other goals identified in the watershed plan.
  2. An estimate of the load reductions expected from management measures.
  3. A description of the nonpoint source management measures that will need to be implemented to achieve load reductions, and a description of the critical areas in which those measures will be needed to implement this plan.
  4. Estimate of the amounts of technical and financial assistance needed, associated costs, and/or the sources and authorities that will be relied upon to implement this plan.
  5. An information and education component used to enhance public understanding of the project and encourage their early and continued participation in selecting, designing, and implementing the nonpoint source management measures that will be implemented.
  6. Schedule for implementing the nonpoint source management measures identified in this plan that is reasonably expeditious.
  7. A description of interim measurable milestones for determining whether nonpoint source management measures or other control actions are being implemented.
  8. A set of criteria that can be used to determine whether load reductions are being achieved over time and substantial progress is being made toward attaining water quality standards.
  9. A monitoring component to evaluate the effectiveness of the implementation efforts over time, measured against the established criteria.

Purpose of Targeting Small Coastal Watersheds

Although this guidebook is designed to be adaptable for use in any coastal watershed, it focuses on devising management plans for watersheds that flow directly into shellfish or swimming waters. These are small drainage areas that are usually much smaller than the 12-digit HUC watersheds that are typically used in watershed planning. Planning on this very small watershed scale allows local leaders to influence change in their area through feasible community-level actions. These small-scale and frequently low-cost actions can have significant positive benefits for the community, including the reopening of closed shellfish waters and a reduction in the frequency of swimming advisories issued for local waters.

Adapting this Guidebook to Your Watershed

While this guidebook is tailored to N.C. coastal subwatersheds, it can easily be used to create a watershed management plan in any coastal watershed throughout the nation where impairments are the result of polluted runoff. The partners and agencies mentioned in this document may not be directly relevant to states outside of N.C., but they can act as suggestions for where to look to find similar information.

There are a handful of state-specific guidebooks that include these elements, so be sure to check if your state already has a planning guidebook.  This guidebook provides N.C. specific resources, organizations, and data sources to ease the planning process.  A successful and effective watershed restoration plan will include, at minimum, the EPA’s nine components but should also include the critical other steps outline in the nine chapters.  It is important to revisit the steps throughout the planning, implementation, and evaluation process, always with the intent of improving the project and achieving restoration goals.

Extensive Water Quality Monitoring Eases Planning Efforts in Coastal N.C.

In N.C., the Shellfish Sanitation and Recreational Water Quality Section (Shellfish Sanitation) of the Division of Marine Fisheries (DMF) is responsible for monitoring the bacteria levels in coastal waters and has the authority to close waters to shellfishing and issue swimming advisories when bacterial levels are unacceptable.  This Section monitors bacterial water quality conditions at over a thousand of stations for shellfishing and 240 stations for swimming. In addition, every three years Section staff walk the entire shoreline of shellfish growing areas to document current and potential pollution sources during their shoreline survey.  The data resources available on the N.C. coast give managers and planners excellent information to affect change without the need for extensive data collection and monitoring.