Riparian Areas: Functions and Conditions

Authors:Gene Surber, MSU ExtensionNatural Resources Specialist

Bob Ehrhart, Research Specialist,RWRP, Univ. of Montana

Riparian AreasWetlands

Riparian areasOverflow areasWet meadowsMarshesSloughs

Characteristics of Riparian Areas

“Green Zone” – link between aquatic and terrestrial

WaterLandformSoilVegetation

Riparian Areas

More dynamic than uplandsFloodingDeposition of sedimentAccumulation of organic matterDewateringChanges in location

Functions of Riparian Areas1. water storage 2. flow energy dissipation3. water quality4. sediment trapping5. bank building and maintenance6. primary biotic production

Store and Release WaterSoil – acts like sponge

Reduces floodingExtends time that surface water is available

Dissipate Energy of Flowing Water

Slows waterVegetationWoody debrisLarge bouldersCobbles

Provide Water QualityNatural pollution control

Trap sediments (nutrients, pesticides, toxic metals, bacteria)

Trap sedimentsTrap sediments – development of new streambanks and bars

Protect soil and waterShields soil and water from:

WindSunlightRain drop impacts

Enhances ProductivityMost productive parts of a landscape

Provide wildlife habitatWater, food, cover and travel routes

BirdsMammalsInsectsFish

Evaluating the Health of Riparian Areas

How well the riparian area carries out the functions

PhysicalBiological

Evaluating Physical Features

Channel downcuttingChannel wideningAmount, location, & causes bare groundAmount of fine materialsAmount of rock

Downcutting“Incisement” = erodes away the channel bottom

Channel becoming wider & shallower

Banks break downStream becomes shallowerStream temperatures rise

Amount, location, & causes of bare ground

Bare ground – erosionNoxious weedsCompaction or bank shearing

Amount of fine materials on channel bottom

Silts, clays, decomposing organic materialNot enough water running

Bank Rock ContentLarge rock versus Sand, silt, small gravelManagement considerations

Biological FeaturesTypes & amounts of plantsHow well they fulfill functionsAmount of foraging & browsingMix of age classes of wood species

Streambank protectionVegetation

Slows velocityStabilizes streambanksReduces erosion

Amount & Types of Vegetation

Canopy cover of desired plantsNoxious weeds

Presence of Trees and Shrubs

Woody plants (trees & shrubs)

Bank stabilizersFood & cover

Determining appropriate presence

Woody species age classDistribution of age class

All old treesAll young trees

Degree of BrowsingExcessive use

(50% of current or previous year’s growth)

Woody DrawsPerform functions of riparian areasHabitat

Cover, food, water

Grazing management plan