Wetlands and Stream Crossings FAQs

An area that, either through surface water or groundwater, is wet enough and wet for a long enough period of time, to support a predominance of vegetation that grows in saturated soil conditions. In order for an area to be deemed a wetland, all three (3) of the following must be present:

• Hydric Soils – Soils that are saturated or flooded during the growing season sufficient to produce anaerobic conditions in the upper soil layers.
• Hydrophytic Vegetation – Greater than 50% of the vegetation present is adapted for life in saturated soil conditions.
• Hydrology – Evidence exists that demonstrates the soils in the area are inundated with water either permanently or periodically throughout the growing season.

Examples of wetlands include, but are not limited to: swamps, bogs, marshes, forested wetlands, wet meadows and vernal pools.

Helpful Documents:

• Recognizing Wetlands (USACE)
• Hydric Soils and Wetland Basics for NH Landowners and Town Officials

NHDES does not provide wetland delineation services. To confirm the presence of a wetland on your property, we recommend contacting a NH Certified Wetland Scientist (CWS).

Ecological Integrity: The ability of an aquatic resource to support and maintain a stable structure of a community of organisms having a specific composition, diversity and functional organization comparable to that of the natural habitat of a region. Proximity of development may alter wetland functions and values. Therefore, evaluation of the resource must consider not only the wetland but also adjacent land use and associated interrelationships.

Wetlands impaired by human disturbance in more developed settings (presence of roads etc.) may provide a lower level of this functional value (or lower ecological integrity condition). Applicants can assess ecological integrity using the New Hampshire Method (2023) or the state Natural Heritage Bureau Ecological Integrity Assessment Manual (2022).
 

Wetlands permits are often required to excavate, remove, fill, dredge or construct structures within certain jurisdictional areas of New Hampshire such as:

• Wetlands, such as forested, scrub-shrub, emergent wetlands, marshes, wet meadows and bogs.
• Surface waters, including the beds and banks of streams, rivers, lakes, ponds and tidal areas.
• Upland Tidal Buffer Zone, which is the area extending landward 100 feet from the highest observable tide line. This area can contain wetlands, transitional areas, developed and undeveloped upland.
• Prime Wetland Buffer, which is the duly established, 100-foot upland buffer surrounding wetlands that have been municipally designated as Prime Wetlands and, at the time of their designation, a 100-foot upland buffer was required.
• Sand Dunes, which are hills or ridges of sand piled up by wind and commonly found on the seacoast.

State statute RSA 482-A does not include wetland setbacks. Some cities and town standards do include wetlands buffers and setbacks, and certain specific resource types in New Hampshire have buffers (added protections). RSA 485-A also includes setbacks for installing new septic systems.

• Prime Wetlands: (RSA 482-A:15) Some municipalities have designated Prime Wetlands. Some have a 100-foot Prime Wetland buffer zone. The Land Resources Management Permit Planning Tool can help applicants determine if a municipality has designated Prime Wetlands with or without 100-foot buffer zones.
• Tidal Buffer Zone: The area extending landward 100 feet from the highest observable tide line may contain wetlands, transitional areas and developed and undeveloped upland.
• The Shoreland Water Quality Protection Act (SWQPA) applies to lakes, ponds and impoundments greater than 10 acres, fourth order and greater streams and rivers, designated rivers and designated river segments, and waterbodies subject to the ebb and flow of the tide.The SWQPA includes a 50-foot primary structure setback and a 20-foot accessory structure setback for accessory structures that are not water-access structures.Tips for vegetation near protected waterbodies are described in a this short video overview and in the Vegetation Management for Water Quality fact sheet.
• Septic Systems: RSA 485-A requires that new septic systems be installed at least 75 feet from wetlands that contain very poorly drained soils and 50 feet from wetlands having poorly drained soils.

When installing septic systems within the protected shoreland, refer to these setbacks.

Within jurisdictional areas, described in state statute (RSA 482-A) and related administrative rules, wetland permits may be required to excavate, fill, dredge, remove or construct structures. Examples may include, but are not limited to:

• Roadways or driveways over wetlands or watercourses.
• New culverts over wetlands or watercourses.
• Driving through wetlands, and/or removing vegetation, when soils are rutted or the roots of vegetation are disturbed.
• Maintaining, repairing or replacing culverts, bridges, dams and other structures.
• Logging activities within wetland areas.
• Trail construction over wetlands or watercourses.
• Utility inspection, maintenance and repair (electric, gas, water) within wetland areas.
• Pond construction and maintenance dredging.
• Beach construction or replenishing beach sand.
• Constructing and repairing boat houses or breakwaters
• Construction, modification and repair of docking structures.
• Installing watercraft lifts.
• Constructing, repairing or modifying retaining walls within or adjacent to surface waters or wetlands.
• Removing sand dune vegetation.

For more information and specific examples, please refer to this short video playlist. 

Temporary wetland impacts are those proposed to be fully restored to pre-construction grades and conditions once permitted work is completed. Examples may include but are not limited to:

• Areas excavated for burying utility lines.
• Ruts caused by heavy machinery that are smoothed and restored when the work is completed.
• Installing temporary equipment access ways.
• Installing temporary erosion and sedimentation controls.

Permanent wetland impacts are those proposed to remain, or that do remain, after the activities have ceased. These include jurisdictional areas that are altered, excavated, dredged or filled to a state that is irreversible. Examples may include but are not limited to:

• Fill associated with a wetland or stream crossing.
• Culverts and excavation associated with ponds.
• Bridge abutments.
• Ditches and channels.

Video: Wetland Permit Applications - Tips for Planning and Design

Most types of wetland permits are valid for five years. Exceptions include, but are not limited to:

• Forestry Statutory Permit-by-Notifications are valid for two years.
• Small Motor Mineral Dredging permits expire at the end of the calendar year in which they are issued.

With some exceptions, such as Forestry Statutory Permit-by-Notifications and Small Motor Mineral Dredging Permits, applicants can request a one-time wetland permit extension, not to exceed five years, provided:

• The permit has not been revoked or suspended without reinstatement.
• Extension would not violate a condition of law (RSA 482-A) or rule (Env-Wt 100-900).
• The project is proceeding towards completion in accordance with plans and other documentation referenced by the permit.
• The applicant proposes reasonable mitigation measures to protect public waters from deterioration during the period of extension.
• The wetland delineation is still valid pursuant to state administrative rules (Env-Wt 406.01(b)).
  
   

Permit applications are required to demonstrate that all proposed impacts to jurisdictional resources such as wetlands will be "avoided and minimized" to the greatest extent practicable.

Avoidance means not impacting jurisdictional areas at all, if an alternative option would have less impact and not have other significant adverse environmental consequences. An example of avoidance is using an available upland area to construct a driveway for a proposed single-family residence to avoid constructing the driveway through a wetland.

If an applicant cannot avoid impacting jurisdictional resources, impacts must be minimized to the greatest extent practicable.

Minimization as used here means reducing adverse impacts to jurisdictional areas such as wetlands. For example, if a wetland crosses an entire property, and an applicant cannot access the buildable portion of the lot without crossing the wetland, minimization measures could include:

• Constructing the crossing through the narrowest portion of the wetland.
• Limiting the number of wetland or stream crossings to the minimum required to access the buildable portion of the lot.
• Narrowing the driveway and side slopes through the wetlands to reduce the amount of fill required.
• Installing culverts to help support hydraulic connectivity and aquatic organism passage.

For more information on how to avoid and minimize impacts for a proposed project, please consult our Wetlands Permitting; Avoidance, Minimization, and Mitigation fact sheet and the 2019 Wetlands Avoidance and Minimization Best Management Practices Manual.

When avoidance and minimization have been exhausted, wetland mitigation may be an option to offset permanent losses of functions and values. It may be required as part of proposed projects to:

• Permanently impact a Priority Resource Area (PRA).
• Permanently impact 10,000 square feet or more of non-tidal wetlands.
• Permanently impact tidal surface waters, tidal wetlands, the tidal buffer zone, or sand dunes, or any combination thereof, unless otherwise specified in state administrative rules Env-Wt. 600.
• Alter the course of or disturb 200 linear feet or more of an intermittent or perennial nontidal stream or river channel or its banks.
• Involve the construction of a new Tier 3 or Tier 4 stream crossing unless otherwise specified in state administrative rules Env-Wt 900.
• Construction of a pond with more than 10,000 square feet of impact in a wetland or surface water.
• Install accessory docking structures or construct new shoreline structures and breakwaters (or includes such work in combination with other qualifying criteria), provided the resulting dock surface area of all shoreline structures on the frontage is 2,000 or more square feet.

To learn more about avoidance, minimization and mitigation, visit the wetlands permit assistance or mitigation pages.

In New Hampshire, a Priority Resource Areas (PRA) is defined in state administrative rules Env-Wt.100 and meets one or more of the following criteria:

• Has documented occurrences of protected species or habitat.
• Is a bog.
• Is a floodplain wetland contiguous to a tier 3 or higher watercourse.
• Is a designated prime wetland.
• Is duly established 100-foot buffer of a designated prime wetlands.
• Is a sand dune, tidal wetland, tidal water, or undeveloped tidal buffer zone.

PRAs in or near proposed project areas may impact their classification or mitigation requirements. Please read the Priority Resource Area fact sheet or watch a short video for more information.

Pre-application meetings are necessary when a project requires mitigation or if a proposed project involves 10,000 square feet or more of potential impacts to wetlands. Please email Rebekah.J.Webb@des.nh.gov for scheduling. Pre-application meetings typically book several weeks in advance. Note that timing will depend on NHDES staff schedules as well as other state and federal agencies if applicable.

Pre-application meetings are also required for streamlined processing of some Minimum Impact projects. Please review the project classification rules that pertain to your project type in Env-Wt 500.

For other project types, pre-application meetings are optional. To schedule one, please contact the applicable Wetlands Regional Reviewer.

Identification of amphibian and invertebrate indicator species and seasonal hydrology are to be evaluated using the following references consistent with the vernal pool definition (Env-Wt 104.44). Using this information, the functions and values of vernal pools in the landscape context can be evaluated, such as wildlife habitat and nutrient export. The Army Corps Vernal Pool Characterization form requires assessment of landscape setting, vernal pool condition, parent material, dominant vegetative community, canopy cover, predominant substrate and pool size. The length of time and portion of the year a vernal pool holds water is important to assess. For more guidance, refer to The Importance of Hydroperiod in Wetland Assessment.

The following documents are guides on documenting the presence of a vernal pool, vernal pool dependent species, the Army Corps characterization form, and an excellent UNH assessment resource on vernal pools.

• Vernal Pool Documentation Manual (NHFG).
• Vernal Pool Assessment and Vernal Pool Characterization Form (USACE).
   

In New Hampshire, as described in state administrative rules Env-Wt. 600 the highest observable tide line (sometimes abbreviated as HOTL) is a line defining the farthest landward limit of tidal flow, not including storm events, that can be recognized by indicators such as the presence of a strand line of flotsam and debris, the landward margin of salt tolerant vegetation, or a physical barrier that blocks farther inland flow of the tide.

Developed upland is an upland area on a lot within the tidal buffer zone or sand dune where:

• The natural soil and vegetation characteristics on more than 50% of the lot have been legally altered and have not returned to a natural state.
• If the lot is in a tidal buffer zone, developed lots abut at least 2 sides of the lot.
• If the lot is in a dune slack area, the lot is surrounded on 4 sides by developed lots or roadways.
• If the lot is in a dune, the back side of a fore dune is within the line of encroachment and the lot is surrounded on 3 sides by developed lots or roadways.
• At least one of the following is true:
  • The lot has legally been filled or excavated in whole or in part, whether prior to jurisdiction or pursuant to a permit or other authorization.
  • The lot contains at least one paved or graded area that is, has been, or will be used for vehicular parking or traffic.
  • One or more residential or commercial buildings has been built on the lot.

Mowing and other cutting of vegetation, including trees, within wet meadows or forested wetlands, is authorized by state administrative rules Env-Wt 309.02(a) if certain conditions are met:

• Roots are not disturbed.
• Ground is frozen or dry enough to avoid making ruts.
• The project is not located in a bog, designated prime wetland, duly established 100-foot buffer, marsh, or tidal buffer zone.

There are limitations on removing vegetation adjacent to many surface waters/ Please refer to this short video or the Vegetation Management for Water Quality fact sheet.

Please note that local town ordinances may also be more stringent than state standards.

BMPs are publications created to promote a better understanding of valuable resources and they provide methods for minimizing impacts to them. Visit the Wetlands Technical Assistance page for a list of wetland BMP resources.

The Natural Heritage Bureau (NHB) maintains data on known locations of rare species and exemplary natural communities. Please use their DataCheck Tool as part of planning proposed projects that require NHDES permits. It will help you confirm the presence or absence of protected species in or near your proposed project area, as well as recommended next steps if you find that any are present.

"Grandfathered" status, in a wetland context, means a structure was in place before its permitting jurisdiction took effect under RSA 482-A:3, I. or its predecessor statute, RSA 483-A:1, I. More information on this topic is described in state rules in Env-Wt 103.58.

To be “grandfathered” as used here, a structure must meet all of the following criteria:

Construction / impact date:

• In and adjacent to tidal waters and wetlands - before June 22, 1967.
• In and adjacent to non-tidal waters and wetlands - before June 2, 1969.
• Seasonal docking structures in tidal or non-tidal waters - before September 4, 1978.
• In duly-established 100-foot buffers - date of designation of associated prime wetlands.

Structure specifics since initial construction and installation:

• Has remained unaltered in location, size and configuration, or is a replacement structure as defined in state rule Env-Wt 104.06.
• Has not been abandoned as defined in state rule Env-Wt 102.02.
• Is consistent with the public’s right to reasonable use of public waters, as established in state case law.
• Is not built on land created by the unauthorized filling of public waters.
  
   

A structure, as defined in RSA 482-A:2, IX, means something installed, erected or constructed in a fixed location. Examples of structures include, but are not limited to: fences, docks, breakwaters, posts, piles, buildings, bridges, culverts and walls.

Structures do not include, provided their construction does not require any regrading or re-contouring of a waterbody’s shoreline and they're not constructed over a waterbody, benches, landings with dimensions no larger than 10 feet wide by 10 feet long, or stairs not wider than 6 feet.

Bankfull width is the distance between the left and right stream banks at bankfull stage (channel forming flow, which is typically the 1.5 to 2-year flood frequency event).

Bankfull depth is the vertical depth of a river/stream channel measured from the bed to the estimated water surface elevation required to completely fill the channel (bankfull width). If water depth exceeds the bankfull depth, then flow would enter onto the floodplain or exit the river/stream channel.

Maximum bankfull depth is measured from the deepest part of the channel (thalweg) to the water surface elevation at bankfull discharge.

Mean bankfull depth is the average depth in a cross-section at bankfull discharge. The bankfull depth corresponds with the start of a floodplain, which can be characterized by the following:

• Topography – usually noted as a berm or a break in the slope from the channel bank to a flatter surface.
• Vegetation – a change from bare surfaces or water tolerant species to semi-water tolerant or upland species.
• Sediment Texture – change in the size distribution of sediments.

In cases where multiple channels exist, bankfull depth is the average depth of all the river/stream channels along a cross section.

Flood-prone width is measured at the water surface elevation that corresponds to twice the maximum bankfull depth.

Entrenchment ratio is calculated as the flood-prone width divided by the bankfull width. Entrenchment ratio is the vertical containment of a river as seen by the relationship between the channel (within the bankfull width) and the surrounding floodplain (within the flood prone width). The lower the ratio, the more entrenched a channel is. Entrenchment ratio helps determine the vertical containment of the river, which should be considered when designing a stream crossing structure.

Sinuosity is a measure of a river's tendency to meander, move throughout a flood plain, or deviate from the shortest possible path. It is expressed as the ratio of actual channel length (AB) to straight-line valley length (CD). The higher the ratio, the more sinuous the stream is.

The Army Corps method is the preferred method and explains how functions can be adapted to the marine or tidal environment. For example, fish and shellfish habitat considers the effectiveness of wetlands, embayments, tidal flats, vegetated shallows and other environments in supporting marine resources such as fish, shellfish, marine mammals and other marine life. 

Bankfull cross-sectional area is the bankfull width multiplied by the mean bankfull depth.

Width to depth ratio is the ratio of the bankfull width divided by the mean bankfull depth.

Where there is a seasonal or permanent watercourse associated with a wetland, the CWS is to use the Army Corps Workbook considerations and qualifiers as they support the wetlands function.

For example, the "fish and shellfish habitat" function considers the effectiveness of watercourses associated with the wetland in question for fish and shellfish habitat. 
 

The applicant is to rely on the primary functions identified by the Certified Wetland Scientist (CWS) for their evaluation report to support the municipally designated prime wetlands and acceptance by NHDES at the time of the designation.

Duly authorized buffer functions are to be assigned based on the relative benefit the duly authorized buffer provides to the adjacent wetland function of the designated prime wetland. 

Wetlands typically have many functions. Sometimes, only one or a few may be considered "principal" functions. The Certified Wetland Scientist (CWS) is to identify which of these functions qualifies as a “principal” function.

Per the Army Corps Highway Method, a "principal" function is defined as an important physical component of a wetland ecosystem (function only) and/or a component considered of special value to society, from a local, regional and/or national perspective. 

More than one principal function may be identified. Even disturbed wetlands in an urban setting can provide principal functions such as water quality attenuation or flood storage functions. Highway Method Workbook Supplement (1999).

Yes, each wetland is to be assigned a principal function. Even disturbed wetlands in an urban setting can provide important water quality attenuation and flood storage function Highway Method Workbook Supplement (1999).