Riparian Corridor Management

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Riparian Corridor Management
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A Little History

• Water has long been the focus of civilizations
• Aquaducts, dams, mills
• The importance of land bordering waterways has
  only recently been appreciated

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What is a riparian corridor?

• Characterized by
• (1) presence of permanent or ephemeral surface or
  subsurface water,
• (2) water flowing through channels defined by the
  local physiography, and
• (3) obligate plants requiring readily available
  water.

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Riparian Corridor Functions

• Water source
• Food supply
• Nutrient and energy flow
• Movement corridors
• Cleanse polluted waters
• Reduce soil erosion and windthrow
• Unique wildlife habitat
• Aesthetics

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Food and Habitat for Wildlife

• Complex food webs derived from diverse vegetation
  and microclimate
• Edge and microhabitats

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Aquatic Food Web
Oxygen, Carbon Dioxide, Heat and Light Energy
Nutrients from the land
Foraging Fish Carnivores, Herbivores, and
Scavengers
Macroinvertebrates Herbivores, Carnivores and
Omnivores
Zooplankton Herbivores and Carnivores
Benthos - Mud Dwelling Scavengers and Decomposers
Algae -Producers
Floating and Submerged Vegetation - Producers
Illustrations by
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Movement

• Mitigate effects of fragmentation

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Cleanse Polluted Waters

• As a filter, suspended materials are removed
• As a transformer, pollutant is chemically altered
• Can also function as a source or sink

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Reducing Erosion

• Stabilize stream banks
• Increase retention time
• Slow runoff
• Decrease effects of flooding

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Management Institutions

• U. S. Army Corps of Engineers
• U. S. Geological Survey
• U. S. Fish Wildlife Service
• National Park Service
• U. S. Environmental Protection Agency
• Natural Resources Conservation Service
• U. S. Forest Service
• Etc., etc.

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Purposes of Management Plan

• Document the condition of the river and corridor
• Document the conditions and trends of resource
  use within the corridor
• Identify threats to the quality of those
  resources
• Identify conflicts of resource protection and
  development
• Present recommendations to the communities

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Key Management Points

• Site specific
• Based on ecological processes
• Consequences beyond the corridor
• Human considerations
• Economics
• Future impacts
• Conservation, management, restoration

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Two Management Locations

• Onsite (within the riparian zone), e.g.
• Grazing management
• Vegetation treatment
• Offsite (outside the riparian zone) change the
  quantity and quality of water entering the
  riparian area, e.g.
• Logging
• Road construction
• Prescribed burning

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Factors to Consider

• Width
• Vegetation
• Canopy Cover

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How wide should the riparian strip be?
Method 1 Constant

• 30 m on each side for streamside zones of mature
  trees
• 100 m for some waterfowl nesting habitat
• 75-100 m for streams and rivers that drain gt130
  sq. km.
• 400 m to maintain wild or scenic corridors

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How wide should the riparian strip be?
Method 2 Scaled to stream order

• First-, second-, third-order small-sized
  streams
• Fourth-, fifth-, sixth-order medium-sized
• Seventh-order and higher large-sized

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How wide should the riparian strip be?
Method 3 Based on stream variables

• Stream width
• Topography
• Soil Type
• Hydrology
• Climate
• Management Goals

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Corridor Width Based On Stream Width

• gt60 m on perennial streams gt10 m wide 30 m on
  streams lt10 m wide 15 m on intermittent streams
• 3X average width of stream at high flow

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Corridor Width Based On Slope

• 15 m on slopes lt10
• 30 m on slopes 10-30
• 46 m on slopes gt30

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Using GIS to Determine Riparian Strip Width
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Using GIS to Determine Riparian Strip Width
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Using GIS to Determine Riparian Strip Width
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What types of vegetation are best for riparian
corridors?

• Vascular aquatic plants have structure and
  physiological adaptations to persist in aquatic
  environments
• Tolerance to flooding

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What types of vegetation are best for riparian
corridors?

• Trees
• Shrubs
• Grasses

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Trees

• Leaves and woody debris resulting in detritus
  layer
• Large organic debris in streams supplied by
  riparian trees influences physical, chemical, and
  biological components of system
• Shade prevents water temperature from reaching
  extremes

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Canopy Cover

• Plan may allow for removal of some timber
• Allowing some sunlight to the floor can increase
  amount of undergrowth
• Vertical structure improves

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Managing Human Disturbance in Riparian Corridors

• Roads
• Fire
• Timber
• Grazing
• Agriculture
• Flow Modification/Regulation
• Urban/Recreational Development

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Management Options

• Complete protection
• Multiple-use approaches
• Exclusive use

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Roads

• Vegetation disturbance
• Increased accessibility
• Soil compaction

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Fire

• Long-term ecological benefits, but
• Short-term risk of erosion

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Timber Cutting in Riparian Corridors

• 75 m strip on larger streams with no cutting in
  the first 25 m then group selection cuts spaced
  at least 30 m apart removing lt50 of canopy in
  rest of buffer
• 100 m strip on larger streams with no cutting in
  the first 50 m selective cutting in next 50 m
• Retain gt50 of basal area within 15-30 m of
  stream
• No harvesting in areas with shallow root systems

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Grazing in Riparian Corridors

• Improper grazing affects channel, streambanks,
  water quality, and vegetation
• Concentrated livestock results in sparse trees,
  compacted soil, and lack of tree production

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Livestock Impacts on Riparia and Streams

• Decreased plant vigor
• Decreased biomass
• Altered species composition and diversity
• Reduction/elimination of woody species
• Elevated surface runoff
• Erosion and sediment delivery to streams

• Stream bank erosion and failure
• Channel instability
• Increased width to depth ratios
• Degradation of aquatic species
• Water quality degradation

Federal Interagency Working Group 1998
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Grazing in Riparian Corridors

• Dont!
• Or at least not within 20 m of stream, and
  controlled beyond that boundary
• Control stocking rates, frequency and duration of
  use, season, access points, and upland forage

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Urban Development
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Recreation

• Increased opportunities for human/wildlife
  contact
• Disturbed habitat
• Soil erosion and compaction
• Loss of vegetation

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The Human Community

• Education
• Receive input
• Address concerns

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Take Home Points for Riparian Corridor Management

• Adaptive
• Sustainable
• Site specific
• Include multiple disciplines
• Communicate

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A thing is right when it tends to disturb the
biotic community only at normal spatial and
temporal scales. It is wrong when it tends
otherwise.