Climate Change


The Mother’s Day storm of 2006 took out this bridge on Connor’s Mill Road in Warner. Replacing failing infrastructure comes at substantial costs. Maintaining our forests along streams upstream of these structures can increase infiltration rates upstream and help minimize these catastrophes. Photo courtesy of Warner Highway Department.


This is a photo of the same storm at the Joppa covered bridge in Warner. The Warner River was not only passing through the bridge, but swelled into its floodplain, cutting off residents beyond from simple travel and emergency services. Photo courtesy of Warner Highway Department.


By contrast, this tributary to the Warner River had no above-ground flow in fall of 2015. This stream location is completely inundated with invasive plant material that overtakes our native plants and even brings whole trees to the ground (as seen upstream in this photo). The combination of lack of forest shade combined with all the excessive cobble deposits indicate the stream is adjusting to a difficult circumstance upstream. In this case, the issue is an I-89 culvert that is perched and over 200 feet long. Just upstream of this location are forested areas that are still cool and largely intact. How amazing it was to rescue a brookie from this tiny puddle!

Keeping abreast of the potential impacts of climate change in New Hampshire is paramount to protecting our ecosystems, our infrastructure, our economy, our children and their future as well as ourselves.

Here are the most recent reports for New Hampshire:
Climate Change in Southern NH
Sea-level Rise, Storm Surge and Extreme Precipitation Events in Coastal NH
Climate Change and Human Health in NH

The US forest Service report Private Forests, Public Benefits: Increased Housing Density and Other Pressures on Private Forest Contributions examines the threat that watersheds throughout the country may experience before the year 2030 due to loss of private forest lands, future housing demands and climate change. This report proposes that the Contoocook River watershed (of which the Warner River watershed is a part) is:

  • The most endangered watershed to suffer the most loss of interior forest;
  • The second most threatened for loss of private forest acreage and water quality; and
  • Ranked ninth nation-wide to experience the most loss of timber volume.

The private and public amenities that our watershed provides, such as clean water, timber, wildlife habitat and recreational opportunities – and our local economy that relies so heavily upon these qualities – is clearly at risk unless we take action and develop in a way that balances housing demands with measures that better protect our watershed resources.


To achieve climate change resiliency within the Warner River watershed, we must take a watershed scale approach. Our efforts must involve our neighbors, multiple towns and multiple agencies to be successful and achieve the funding necessary to make needed changes. By working together we will sustain our wild brook trout and our high water quality.

Wild Brook Trout Habitat Threats & Opportunities given Climate Change
Anglers and conservationists across the country and throughout the world are speaking out in an effort to preserve aquatic habitat for wild brook trout, salmon and other species at risk due to the impact climate change is already having on our ecosystems, and the future changes scientists predict. Wild brook trout are connoisseurs of clean, clear, coldwater habitats. They are so discerning, the EPA regards them as a marker species for high quality watersheds. To learn more about wild brook trout,  their habitat requirements and their vulnerability to climate change, see our About Wild Brook Trout.

Below are climate change threats and opportunities to preserve our native stream dwellers and our watershed health.

Habitat Degradation Associated with Acid Deposition 
Acid deposition (acidic pollutants delivered to our soils and streams by air and rain) has extirpated or reduced population densities of brook trout and other species in the northeast, especially in naturally acidic small streams and ponds at high elevations. Episodic acidification of small streams has been shown to reduce brook trout densities and cause fish to seek refuge downstream in streams with higher pH. Yet downstream temperatures tend to rise, so where do these fish go to survive? Overall, episodes of acid rain are being reduced by tighter regulations on coal plants, but the buffering capacity of watersheds where calcium has been leached from the soil may not recover on its own. Vermont’s geology and soils have higher ability to buffer and recover from this damage. New Hampshire’s surficial geology and soils, by contrast, tend to be more acidic naturally, so our environmental recovery takes much, much longer.

Higher Intensity Storms, Increased Flooding & Higher Water Temperature                   
Changes in flow conditions due to climate change may alter seasonal flow patterns as well as the intensity and frequency of flood events. Increased water temperature can increase mortality or restrict the seasonal movements of native aquatic species and also shift community assemblages. Damage to aquatic habitats from increased flooding is often exacerbated by human activity. Efforts to protect infrastructure and property in floodplains, by installing armoring and diversion structures, have increased ecological damage to river and stream habitat during recent floods in New Hampshire.

Preserve and Restore Riparian Buffer Protection is the most effective and economically feasible practice to protect aquatic habitat and water quality. Forested stream buffers can be achieved through voluntary land use practices (such as agricultural and forestry best management practices), town ordinances, state law (i.e. The Shoreland Water Quality Protection Act and the Rivers Management and Protection Program (RMPP), deed restriction and conservation easements.

In general, the wider forested stream buffer, the greater the ecological benefit. A forested buffer of at least 10 m (32.8 ft) will provide a minimum level of water quality and habitat benefits. A 2014 scientific article in the Journal of the American Water Resources Association, Streamside Forest Buffer Width Needed to Protect Stream Water Quality, Habitat, and Organisms: A literature Review, evaluated riparian buffer width effectiveness using eight different criteria to determine the best width for protecting habitat and water quality. They determined that for the size of the Warner River and smaller streams, widths 30 m (98.4 ft) or more is necessary to protect the physical, chemical and biological integrity. A protected buffer of 100 m (328 ft) or greater provides maximum water quality and habitat benefits while also acting as a migration corridor for larger species of wildlife. Buffer protection is lacking on headwater streams despite the cumulative effect that intact riparian zones in headwater streams have on downstream water quality.

TU’s 2nd Edition of My Healthy Stream – A Handbook for Streamside Owners is an outstanding resource for municipalities, residents, landowners and volunteers seeking to learn how to best steward over our watersheds and brook trout streams. Be sure to checkout the helpful companion PowerPoint presentation on the same web page. Basil Woods TU has hard copies of My Healthy Stream available, please contact us if you would like a copy.
The Shoreland Water Quality Protection Act
Rivers Management and Protection Program (RMPP)

Reconnect Floodplains & Restore Meanders – Floodplains allow rivers and streams to disperse flows and dissipate energy during flood events. River and stream habitat is frequently altered in an effort to control or prevent flood damage to local infrastructure. Channel straightening, bank armoring, berm construction, and other practices result in a confined stream channel that no longer has access to floodplain habitat. These practices result in a loss of important habitat features, such as undercut banks, large in‐stream wood, and stream-side vegetation. While achieving the goal of protecting infrastructure at one location, these practices often exacerbate flooding downstream. Often done in response to recent flooding, river and stream bank modifications are rarely completed according to a long term plan that attempts to combine river restoration and flood prevention. Efforts to address flood damage should be evaluated at the watershed level.

Flooding during Hurricane Irene caused severe flood damage in northern New Hampshire and Vermont. Much of this damage was exacerbated by river and stream channel alterations to protect infrastructure and property in floodplains. Attempts to rebuild structures that would accommodate more stream flow and improve habitat for aquatic species were hindered by reimbursement requirements for the Federal Emergency Management Agency. Active floodplain areas should be mapped and left intact. Damage to roads and other structures would be minimized if active floodplain areas were avoided.

Living in Harmony with Streams: A Citizen’s Handbook to How Streams Work (2012)
New Hampshire Guidelines for Naturalized River Channel Design and Bank Stabilization
New Hampshire River Restoration and Fluvial Geomorphology
NRCS Stream Restoration Design Handbook
Flood Hazards, Rivers and the Clean Water Act

Replace Undersized Culverts at Road-Stream Crossings – Poorly sized stream crossings alter the natural sediment transport characteristics of a river or stream, which leads to erosion and excess sediment deposition in the stream channel. The cumulative effect of under sized stream crossings can lead to increased sedimentation and turbidity throughout a watershed during storm events. Road fill from washed out stream crossings during flood events accumulates in the stream channel and buries the natural stream bed substrate. Observations of stream crossings during fish surveys in New Hampshire suggest that there are very few streams that do not show some habitat damage from stream crossings.


Perched culverts prevent fish from reaching critical spawning and nursery habits. In addition, water gains velocity and more turbulence occurs, increasing flood risk.

Undersized stream crossings can function as a barrier to the movement of aquatic species and often constrict flows, creating an increase in flow velocity through the structure. As a result, increased scour at the structure outlet occurs and a drop or “perch” is formed between the stream bed and bottom of structure. Many stream crossings restrict aquatic organism movement at certain flows due to high velocities, insufficient depth within the crossing, or an outlet that consists of a small waterfall. These barriers prevent access to critical habitat, reduce gene flow, and result in local extirpations of isolated populations. A number of studies have demonstrated reductions in fish species richness and abundance upstream of impassable stream crossings

There are two phases to stream crossing restoration. The first phase is assessment. Stream crossing surveys are currently being completed in watersheds throughout the state. It is important that these surveys follow the standardized methods and protocols outlined by the New Hampshire Geological Survey (NHGS). NHGS maintains a statewide database of stream crossing survey data. Once the data is collected, stream crossing restoration projects can be prioritized to achieve the greatest benefits to aquatic organism passage, along with reductions in flood damage and habitat degradation. Prioritization may take place within small watersheds or across a large region. The second phase is implementation. Once a stream crossing is identified as a good candidate for restoration there are many obstacles to a completed project, including fund raising, permitting, and cost. Streamlining the permitting process for crossing restoration, increasing available funding sources, and developing innovative stream crossing design and construction techniques that significantly reduce cost would greatly increase the number of stream crossing restoration projects in New Hampshire.

Guidelines for Streams & Stream Crossings
NH DES Streams & Stream Crossings
NH’s Streamcrossing (Culvert) Assessment Protocol
NH’s Stream Crossing Guidelines

Ongoing Successful Projects
New England Culvert Project (TU)
Assessing Flood Risk in the Lamprey River Watershed 
Nash Stream Restoration, Connecticut River Watershed, NH
Clark Brook, Oliverian Brook & Eastment Brook, Connecticut River Watershed, NH
Eastside Road Floodplain Restoration Project, White Mountain National Forest, NH
UNHSC’s Urban Watershed Renewal in Berry Brook, an Examination of Impervious Cover, Stream Restoration and Ecosystem Response, Dover, NH

Increased Stormwater Runoff & Pollution from Impervious Surfaces                 
Storm water runoff from hot, paved or otherwise impermeable surfaces change the hydrology and water chemistry of local rivers and streams. Flashier storm flows cause an increase in erosion and sediment deposition along stream banks and in the stream channel. More surface flow can lead to a decrease in groundwater infiltration, which results in lower stream flows during dry periods. Oil based pollutants, sediment, and road salt are washed from roads and parking lots into surrounding waterbodies which can lead to chronic declines in water quality. Runoff from pavement and roofs warmed by the sun can also lead to increased water temperatures in local streams when stormwater flows directly into surface waters.

STORM GI_21 TB reaingarden UNH

This UNH rain garden captures, infiltrates and treats storm water runoff from this parking lot. (Photo courtesy of UNH Stormwater Center)

STORM GI_22 TB rain gradens UNH

The same rain garden in bloom during the growing season adds an attractive element to the parking lot.(Photo courtesy of the UNH Stormwater Center)

Stormwater runoff from impervious surfaces has been shown to damage aquatic habitats. Much of this damage can be prevented by storm water management practices that filter runoff through the ground before it enters surface water. This practice not only removes much of the sediment and toxins that are typically washed into streams, but it also reduces the rapid fluctuation in temperature, as well as the excess erosion and sediment deposition that have become a chronic issue for rivers and streams in developed areas.

Minimize Point-Source Pollution (pipes that discharge directly into our waterbodies)Industrial pollutants and pollution that directly discharge untreated wastewater into waterbodies from pipes have been greatly reduced since the passage of the Clean Water Act. However, there are still isolated areas such as Superfund Sites or combined sewer overflows (CSO’s) where pollutants continue to enter aquatic habitats at known locations.

STORM GI_23B rain-garden-2

Rain gardens can also be installed to treat stormwater runoff from streets and driveways. (Photo courtesy of UNH Stormwater Center)


Install Low Impact Development (LID) techniques and Green Infrastructure (GI) (like rain gardens and tree box filters to infiltrate stormwater where it falls, thereby allowing soil microorganisms to break down pollutants and cool stormwater temperature before reaching our rivers and streams.

Resources for Pollution & Stormwater Management

New Hampshire Homeowner’s Guide to Stormwater Management (2016)
New Hampshire Stormwater Manual
Landscaping at the Water’s Edge
NH Soak Up the Rain a great resource for homeowners.
UNH Stormwater Center (UNHSC)leads the nation for their research and implementation of Low Impact Development (LID) practices for stormwater management.
UNHSC’s Thermal Impacts, Stormwater Management, and Surface Waters

Successful Watershed Projects Utilizing LID techniques to Improve Watershed Health
UNH SC’s Urban Watershed Renewal in Berry Brook, an Examination of Impervious Cover, Stream Restoration and Ecosystem Response, Dover, NH

McQuesten Watershed Restoration Project

Exotic Aquatic and Terrestrial Invasive Species & Disease
Higher temperatures and shorter winters combined with a longer, warmer growing season will allow for pests and non-native plants to move northward more easily.

Exotic Aquatic Species – Whether they are accidental or intentional, invasive aquatic species introductions are notoriously difficult to prevent and even more difficult to control. NHDES, NH Lakes Association and other individual lake and pond groups have had some success preventing invasive aquatic species introductions with public outreach and by staffing boat ramps with trained inspectors, called Lake Hosts. Prevention and early detection is the most effective strategy for limiting the spread of invasive species. Once an introduced species has become established it is nearly impossible to eradicate it. Management efforts to control the species can be costly and requires long term planning.

An angler determined to create a new fishing opportunity by stocking a new fish species into a waterbody is hard to deter. Education on the ecological damage that can be caused by introducing nonnative species into a waterbody will help prevent some, but not all deliberate species introductions. In some cases, anglers invested in the existing fishery may make the best advocates against new species introductions. However, outreach will not persuade everyone, so laws, penalties, and adequate funding for enforcement are the last line of defense against species introductions. It is important that penalties are severe enough and the presence of law enforcement is noticeable enough to act as a deterrent. New species introductions are inevitable, but the rate and overall extent of introductions may be contained.

Prevent spread of these species by cleaning, draining and drying your boat, your boots and fishing gear to prevent spreading invasives from one waterbody to another. Learn to identify species and reporting infestations to your local conservation commission.

Become a Citizen Scientist or NH Rivers Council River Runner to be able to identify invasive species when you are kayaking, fishing or hiking in the watershed.

Early Detection & Distribution Mapping (EDD Maps) provides both an online and mobile app resources that aid in field id and reporting of any kind of invasive plant or species. Locations and sizes of infestations can be mapped to improve communication and coordinate eradication efforts across multiple parties and agencies.

Resources Pertaining to Aquatic Invasive Plants & Species

Exotic Terrestrial Species – These alien plant species take advantage of our ecosystems in the same way as aquatic plants, although typically take root along our major highways, public utility corridors and other areas of land disturbance.

Exotic Insects & Diseases

  • NH Bugs provides up-to-date information on Damaging Insects and Diseases in NH