Wetland Functions and ValuesWetland Functions and ValuesFundamentals for Conservation Commissioners

Training Program - Unit 5

Fundamentals for Conservation CommissionersTraining Program - Unit 5

Massachusetts Association of Conservation CommissionsMassachusetts Association of Conservation Commissions

Creation of this Unit was funded in part with a grant

from the Massachusetts

Environmental Trust.

Creation of this Unit was funded in part with a grant

from the Massachusetts

Environmental Trust.

Developed by Scott Jackson of

the University of Massachusetts

Developed by Scott Jackson of

the University of Massachusetts

Wetland ValuesWetland Values

• Flood control

• Storm damage protection

• Pollution control

• Protection of water supply

• Protection of groundwater

• Fisheries and shellfish

• Wildlife habitat

• Climate regulation

• Aesthetics and recreation

• Education and research

• Harvest of natural products

Interests Protected by the ActInterests Protected by the Act

• Flood control

• Storm damage prevention

• Pollution prevention

• Public and private water supply

• Groundwater supply

• Land containing shellfish

• Fisheries

• Wildlife habitat

Salt MarshSalt Marsh

BogBog

Forested SwampForested Swamp

Floodplain ForestFloodplain Forest

Shrub SwampShrub Swamp

MarshMarsh

Wet MeadowWet Meadow

Wetland ValueWetland Value

Wetland FunctionWetland Function

Capacity:

Wetland Characteristics

Capacity:

Wetland Characteristics

Opportunity:

Watershed Context

Opportunity:

Watershed Context

Flood Control: FunctionFlood Control: Function

• Flood storage (reduces flood peaks)

• Velocity reduction (reduces flow)

• Desynchronization (staggers flood peaks)

Flood Control: CharacteristicsFlood Control: Characteristics

• Capacity for ponding or flooding

• Flood ratio

• Size

• Associated with watercourse

• Constricted outlet

• Sheet vs. channelized flow

• Dense vegetation (forest or shrub)

• Roughness

Flood Control: Watershed ContextFlood Control: Watershed Context

• Located just upstream of human settlements or other sensitive areas

• Large proportion of impervious surfaces

• Large proportion of steep slopes

• Channelized waterways into wetland

• Lakes & wetlands <10% of watershed

Storm Damage Control: FunctionStorm Damage Control: Function

• Anchor shoreline

• Dampen waves

• Reduce current velocity

• Intercept water

Storm Damage Control: Characteristics

Storm Damage Control: Characteristics

• Associated with watercourse or water body

• Dense Vegetation

• Wetland width >10'

• Gradual shoreline (erosion)

• Gradient in wetland (waves)

Storm Damage Control: Watershed Context

Storm Damage Control: Watershed Context

• Coastal areas

• Open water fetch >2000 ft.

• High water velocities

• Downstream of channelized waterway

• Downstream of water release dam

• Potential for boat wakes

• Physical

• Chemical

• Biological

Pollution Control: FunctionPollution Control: Function

Wetlands remove pollutants using

several processes

Important PollutantsImportant Pollutants

• Toxic materials

• Sediment

• Nutrients

Pollution Control: CharacteristicsPollution Control: Characteristics

• Capacity for ponding or flooding

• Flood ratio• Water retention• Constricted outlet• Gentle wetland

gradient• Sheet vs. channelized

flow• Size

• Aerobic/anaerobic soil interface

• Duration saturation/shallow inundation

• Dense vegetation (floating, emergent)

• Organic soils• Shellfish beds

Pollution Control: Watershed Context

Pollution Control: Watershed Context

• Upstream of water supply or other sensitive areas

• Proximity to pollution sources

• Large proportion of impervious surfaces

• Lakes & wetlands <10% of watershed

Protection of Water Supply: FunctionProtection of Water Supply: Function

Water Quality

• Removing pollutants

Water Quantity

• Detaining and releasing runoff and floodwater

• Groundwater discharge

Groundwater Discharge: IndicatorsGroundwater Discharge: Indicators

• Presence of springs

• Surface outflow exceeds surface inflow

• Persistent flow

• Consistent water temperature

• Outlet only

• Topographic position

• Large size relative to catchment area

Soil horizon(inches below

surface)

Horizontalwater flow rate(inches/hour)

Reduction inflow rate(percent)

Degree ofdecomposition

(1 to 10)

0-3 250 0 13-6 140 44 26-9 63 75 39-12 21 92 4

12-18 7 97 518-24 3 99 6 & 7

Boelter and Verry 1977

Horizontal Water Flow Rate as a Function of Depth Below the Surface in Organic WetlandsHorizontal Water Flow Rate as a Function of Depth Below the Surface in Organic Wetlands

Protection of Water Supply: Watershed Context

Protection of Water Supply: Watershed Context

• Located in deposits of stratified drift

• Upstream of water supply or other sensitive areas

• Proximity to pollution sources

• Large proportion of impervious surfaces

• Lakes & wetlands <10% of watershed

Protection of Groundwater: Function

Protection of Groundwater: Function

• Removing pollutants

• Groundwater recharge

Groundwater Recharge: Mechanisms

Groundwater Recharge: Mechanisms

• Perched wetlands

• Floodplains

• Bank storage

• Seasonal recharge

Confining Layer (hard pan)Confining Layer (hard pan)

Aquifer

Water Table

Recharge

Perched WetlandPerched Wetland

Bank StorageBank Storage

Recharge

Flood Level

Normal Water Level

Impervious Wetland Soil

Pervious Soil

Groundwater Recharge: Characteristics

(where recharge function is present)

Groundwater Recharge: Characteristics

(where recharge function is present)

• Association with watercourse

• Perched wetland

• Somewhat permeable soils

• Variable water levels

• High edge-to-volume ratio

Protection of Groundwater: Watershed Context

Protection of Groundwater: Watershed Context

• Public or private wells down gradient

• Significant wetlands or watercourse down gradient

• Proximity to pollution sources

• Large proportion of impervious surfaces

• Associated with a significant aquifer

• Located in deposits of stratified drift

Shellfish Habitat: FunctionShellfish Habitat: Function

• Provide appropriate substrates

• Food chain support

• Maintenance of water supply

• Maintenance of water quality

POM

NO2

Food Chain SupportFood Chain Support

PlantsNutrient Uptake

OrganicDebris

InvertebratesDebris Processing

Shellfish Habitat: Characteristics(coastal areas and directly upstream)Shellfish Habitat: Characteristics(coastal areas and directly upstream)

• Salt marsh and/or tidal flats present

• Unrestricted tidal hydrology

• Water quality

• Productivity/POM export

• Connection with waterway supporting shellfish

• Capacity to remove pollutants

Fish Habitat: FunctionFish Habitat: Function

• Spawning areas

• Nursery habitat

• Cover

• Food chain support

• Maintenance of water supply

• Maintenance of water quality

Fish Habitat: CharacteristicsFish Habitat: Characteristics

• Connection with permanent water

• Presence of springs

• Water chemistry

• Temperature

• No channelization

• Pools at low water

• Natural fluctuation in water level

• Cover and shade

Wildlife Habitat: FunctionWildlife Habitat: Function• Breeding areas

• Foraging areas

• Shelter

• Over-wintering areas

• Migratory routes

• Food chain support

• Maintenance of water supply

• Maintenance of water quality

Wildlife Habitat: CharacteristicsWildlife Habitat: Characteristics

• Diversity of wetland classes

• Interspersion of vegetation and open water

• Diversity of vegetation (vertical and horizontal)

• Surrounding habitat

• Water chemistry

• Scarcity

• Special habitat features

Wildlife Habitat: Examples of Special Habitat Features

Wildlife Habitat: Examples of Special Habitat Features

• Vernal pools• Saltwater pans• Mud flats• Undercut banks• Vertical sandy banks• Underwater banks of fine silt &

clay• Sphagnum hummocks and pools• Large cavity trees

Special HabitatFeatures

Special HabitatFeatures

Special HabitatFeatures

Special HabitatFeatures

New Hampshire MethodNew Hampshire Method

New Hampshire Method:Ground WaterUse Potential

New Hampshire Method:Ground WaterUse Potential

Buttonbush

River

Open WaterMarsh

Gas Pipeline(Limited Project)

Floodplain Forest

DetentionBasin

Mall

Parking Lot

ForestedSwamp

PermanentOpen Water

Perennial Stream

Access Road

ReplicationArea