Riparian Areas: Functions and Conditions
Authors:
Gene Surber, MSU Extension
Natural Resources Specialist
Bob Ehrhart, Research Specialist,
RWRP, Univ. of Montana
Riparian Areas
Wetlands
Riparian areas
Overflow areas
Wet meadows
Marshes
Sloughs
Characteristics of Riparian
Areas
“Green Zone” – link between aquatic
and terrestrial
Water
Landform
Soil
Vegetation
Riparian Areas
More dynamic than uplands
Flooding
Deposition of sediment
Accumulation of organic matter
Dewatering
Changes in location
Functions of Riparian Areas
1. water storage
2. flow energy dissipation
3. water quality
4. sediment trapping
5. bank building and maintenance
6. primary biotic production
Store and Release Water
Soil – acts like sponge
Reduces flooding
Extends time that
surface water is available
Dissipate Energy of Flowing
Water
Slows water
Vegetation
Woody debris
Large boulders
Cobbles
Provide Water Quality
Natural pollution control
Trap sediments
(nutrients,
pesticides, toxic
metals, bacteria)
Trap sediments
Trap sediments – development of new
streambanks and bars
Protect soil and water
Shields soil and water from:
Wind
Sunlight
Rain drop impacts
Enhances Productivity
Most productive parts
of a landscape
Provide wildlife habitat
Water, food, cover
and travel routes
Birds
Mammals
Insects
Fish
Evaluating the Health of
Riparian Areas
How well the riparian area carries out
the functions
Physical
Biological
Evaluating Physical Features
Channel downcutting
Channel widening
Amount, location, & causes bare ground
Amount of fine materials
Amount of rock
Downcutting
“Incisement” = erodes away the
channel bottom
Channel becoming wider &
shallower
Banks break down
Stream becomes
shallower
Stream
temperatures rise
Amount, location, & causes of
bare ground
Bare ground – erosion
Noxious weeds
Compaction or bank shearing
Amount of fine materials on
channel bottom
Silts, clays, decomposing organic
material
Not enough water running
Bank Rock Content
Large rock versus
Sand, silt, small gravel
Management considerations
Biological Features
Types & amounts of plants
How well they fulfill functions
Amount of foraging & browsing
Mix of age classes of wood species
Streambank protection
Vegetation
Slows velocity
Stabilizes streambanks
Reduces erosion
Amount & Types of Vegetation
Canopy cover of desired plants
Noxious weeds
Presence of Trees and Shrubs
Woody plants (trees &
shrubs)
Bank stabilizers
Food & cover
Determining appropriate
presence
Woody species age class
Distribution of age class
All old trees
All young trees
Degree of Browsing
Excessive use
(50% of current or previous year’s growth)
Woody Draws
Perform functions of
riparian areas
Habitat
Cover, food, water
Grazing
management plan