Riparian Forest Buffers

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Riparian Forest Buffers

• Def. land adjacent to a waterway is referred to
  as the riparian zone.
• Other terms used riparian management zones
  (RMZ) or streamside management zone (SMZ)

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Benefits

• Control surface runoff and shallow ground water
• Nutrients
• Sediment
• Shade streams
• Ameliorate effects of some pesticides
• Provide dissolved and particulate organic food
  for aquatic and terrestrial systems

Sheet erosion on crop land
3
Shallow Groundwater

• Frequently occurs in riparian areas
• Saturated condition which occur near or within
  the root zone of trees and other woody vegetation
  and at relatively shallow depths where bacteria,
  oxygen, and soil contribute to denitrification

4
Nonpoint Source Pollution

• NPS pollution is caused by rainfall or snowmelt
  moving over and through the ground.
• As the runoff moves, it picks up and carries
  away natural and human-made pollutants, finally
  depositing them into lakes, rivers, wetlands,
  coastal waters, and even our underground sources
  of drinking water.

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Nonpoint Source Pollution (NPS)

• NPS Pollutants include
• Excess fertilizers, herbicides, and insecticides
  from agricultural lands and residential areas
• Oil, grease, and toxic chemicals from urban
  runoff and energy production
• Sediment from improperly managed construction
  sites, crop and forest lands, and eroding stream
  banks
• Salt from irrigation practices and acid drainage
  from abandoned mines
• Bacteria and nutrients from livestock, pet
  wastes, and faulty septic systems
• Atmospheric deposition and hydromodification.

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NPS Hydromodification

• Hydrography
• Configuration of an underwater surface including
  its relief, bottom materials, coastal structures,
  etc.
• Description and study of seas, lakes, rivers, and
  other waters.

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NPS Hydromodification
During
Before
Bear Creek, Blackfoot River, Montana
After

• Hydrologic modification
• The alteration of the natural circulation or
  distribution of water by the placement of
  structures or other activities

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NPS Hydromodification

• Alteration of the hydrologic characteristics of
  coastal and noncoastal waters, which in turn
  could cause degradation of water resources

Undersized and perched culvert on
McCabe Creek before restoration
Open bottom box culvert on McCabe Creek after
restoration
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Example of Hydromodification

• Streambed scouring and bank erosion resulting
  from storm surges within urbanized watersheds

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NPS Sediment

• Total suspended solids (TSS), i.e., sediment is
  major NPS pollution of concern

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NPS Phosphorus

• Major nutrient leading to water pollution
• Leads to low dissolved oxygen from excessive
  plant growth
• Binds to soil particles

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NPS Nitrogen

• Water soluble
• Some converted to gaseous forms by microbial
  action
• Enters surface and goundwater

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Underlying Principles of Buffers

• Vegetation and soil filters sediments
• Vegetation takes up nutrients which can be
  removed from portion of site by harvesting timber
  and forage.

Clearfield Creek in PA, stable structure but
polluted by mine drainage
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Streamside Forest as Sediment Filter

• Sediment settles as speed of surface flow reduced
  by forest floor
• Sediment is filtered out as sediment loaded water
  percolates into porous forest floor

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Riparian Forest Buffer

• Forest dominated landscapes
• Leave continuous unharvested forest along
  waterways
• Agriculture dominated landscapes
• Create 3 zone buffer along waterways

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Riparian Forest Buffer

• Where to use
• Adjacent to permanent or intermittent streams
  occurring at lower edge of upslope crop land,
  grassland or pasture, or harvested forest
• Margin of lake or ponds

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Riparian Forest Buffer

• Where to use
• Margin of intermittent or permanently flooded,
  environmentally sensitive open water wetlands
• On karst formations at margins of sinkholes and
  other groundwater recharge areas

A deep sinkhole
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Riparian Forest Buffer

• Use to protect any water body which will not be,
• Routed through a natural or artificial wetland
  serving as an adequate nutrient sink
• Where concentrated flows will not otherwise be
  converted to sheet flow and routed through a
  forest buffer at a lower point in the watershed.

Need to exclude livestock, provide access by
piping water to tank, and planting buffer.
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Riparian Forest Buffer Design

• Objective - encourage sheet flow and infiltration
  and impede concentrated (stream like) flow
• Consist of 3 zones
• Undisturbed forest
• Managed forest
• Grassland

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Riparian Forest Buffer Design
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Riparian Forest Buffer Zone 1

• Location from top of stream bank outward at
  least 15 ft.
• Purpose create stable ecosystem adjacent to
  waterway
• Shade watercourse
• Contribute detritus and large woody debris to
  steam ecosystem

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Riparian Forest Buffer Zone 1

• Function handle sheet and subsurface flows only
• Limits
• No subsurface drains that bypass this zone
• No grazing but maintained stream crossings
  allowed
• Vegetation mix of native riparian tree and
  shrub species

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Riparian Forest Buffer Zone 1

• Management
• Large over mature trees left to fall
• Occasional removal of high value trees permitted
  if disturbance is very limited
• Equipment excluded except for necessary stream
  crossing and stabilization work

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Riparian Forest Buffer Zone 2

• Location Minimum of 60 ft. beyond edge of zone
  1
• Purpose
• Provide necessary contact time
• Provide carbon energy source for buffering and
  long-term sequestering of nutrient
• Function
• Handle sheet and subsurface flows

Buffered rangeland.
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Riparian Forest Buffer Zone 2

• Limits
• Any subsurface drains should be converted to
  sheet flow in zone 3
• No grazing, but maintained stream crossing
  allowed
• Vegetation
• Native riparian tree and shrub species
• No nitrogen fixers if nitrogen buffering is needed

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Riparian Forest Buffer Zone 2

• Management
• Periodic harvesting and TSI to maintain vigorous
  growth and to remove sequestered nutrients.
• Can manage for wildlife habitat and aesthetics
  as long as production of leaf litter, detritus
  and large woody debris is maintained
• Appropriate equipment allowed as necessary

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Riparian Forest Buffer Zone 3

• Location
• Minimum of 20 ft. beyond edge of zone 2, or wider
  to accommodate whatever mowing equipment is to be
  used
• Purpose
• Sediment filtering
• Nutrient uptake
• Function
• Convert concentrated flow to uniform shallow,
  sheet flow using grading, shaping, diversions
  basins and level lip spreaders

Well vegetated buffer in southwest US.
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Riparian Forest Buffer Zone 3

• Limits
• Activities that would damage earthworks
• Vegetation
• Dense grass and forbs for structure
  stabilization, sediment control and nutrient
  uptake.
• Management
• Mow and remove, or use controlled intensive
  grazing, to maintain vigorous growth and remove
  nutrients
• As necessary reshape earthworks, remove
  accumulated sediment and reestablish vegetation

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Total Buffer Width Streamside

• Determine based on
• Soil hydrographic group
• Total area of source
• Soil capability class

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Soil Hydrologic Groups
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Total Buffer Width Streamside

• Soil Hydrologic Group
• Widen zone 2 to include all group C and D soils
  subject to frequent flooding
• 75 ft. minimum for zones 1 and 2 applies to group
  A or B soils adjacent to intermittent or
  perennial streams

33
Total Buffer Width Streamside

• Source area
• Increase zone 2 for combined zone 1 and 2 width
  of 1/3 of slope distance from stream bank to top
  of pollution source area, i.e.
• Total buffer between field and forest will be 1/3
  of source area

Incomplete streamside buffer
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Total Buffer Width Streamside

• Soil capability class
• Increase width of zone 2 to provide combined
  width of zone 1 and 2 of,

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Soil Capability Classes

• Indicates the suitability of soils for
  agriculture.
• The soils are grouped primarily by their
  capability for sustained production of cultivated
  crops and pasture plants. They are grouped by 2
  levels, class and subclass, to indicate the
  degree and kind of major soil limitations.
• Classes -- the broadest groups (typically
  designated by Roman numerals I to VIII) the
  numeral indicate progressively greater
  limitations and narrower choices for agriculture.

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Soil Capability Classes

• Subclasses Groups of (soil) capability units
  within classes of the land capability
  classification that have the same kinds of
  dominant limitations for agricultural use as a
  result of soil and climate.
• The four kinds of limitations recognized are
• risks of erosion (e)
• wetness, drainage, or overflow (w)
• other root zone limitations (s) and
• climatic limitations (c).

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Total Buffer Width Pond and Like-Side

• Buffer area should be at least 1/5 drainage area
  of cropland and pastureland source area.
• Width determined by creating uniform width buffer
  of total required area
• Hydrologic and capability class methods for
  streamside buffers applies.

Houses, not cropland, are major source of lake
pollution in midwest.
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Total Buffer Width Wetlands

• Focus
• Wetlands adjacent to open water and subject to
  flushing, not those functioning as nutrient sinks
• Buffers should have zones 1, 2 and 3 on sides
  receiving runoff

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Indiana BMP RMZ Width Recommendations
Total RMZ Width
Width in feet on each side of watercourse
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Midwest Issue

• Field drain tiles empty into drainage ditches
  that flow directly to waterways.
• Methods need to buffer tile water before it
  enters ditches.

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Midwest Issue

• A solution being studied
• Run ditch water through constructed or natural
  wetland before entering waterway
• Use these wetlands for production of hydrophytic
  crops and for-fee waterfowl hunting

Forest wetlands can also function as nutrient
sinks.