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