riparian forest buffers def. – land adjacent to a waterway is referred to as the “riparian...

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)

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

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

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.

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.

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.

NPS: Hydromodification

• Hydrologic modification:– The alteration of the natural

circulation or distribution of water by the placement of structures or other activities

Bear Creek, Blackfoot River, Montana

Before During

After

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

Example of Hydromodification

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

NPS: Sediment

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

NPS Contribution of Total Suspended Sediment (TSS), 1980

Cropland 38%

Pasture and range25%

Forest5%

Background26%

Other6%

NPS: Phosphorus

• Major nutrient leading to water pollution

• Leads to low dissolved oxygen from excessive plant growth

• Binds to soil particles

Sources of NPS Phosphorus

Cropland41%

Forest2%

Background28%

Other1%

Pasture and range28%

NPS: Nitrogen

• Water soluble• Some converted

to gaseous forms by microbial action

• Enters surface and goundwater

Sources of NPS Nitrogen

Cropland43%

Pasture25%

Forest4%

Background25%

Other3%

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

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

Riparian Forest Buffer

• Forest dominated landscapes– Leave continuous

unharvested forest along waterways

• Agriculture dominated landscapes– Create 3 zone buffer

along waterways


• 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


• 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


• 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.

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

Riparian Forest Buffer: Design

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


• 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


• 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


• 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 flowsBuffered rangeland.


• 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


• 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


• 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.


• 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

Total Buffer Width: Streamside

• Determine based on – Soil hydrographic

group– Total area of source– Soil capability class

Group

Type

Infiltration capacity/permeability

Leaching potential

Runoff potential

Adeep, well-drained sands and gravels

high

High

low

Bmoderately deep to deep, moderately drained, moderately fine to moderately coarse texture

moderate

moderate

moderate

Cimpeding layer, or moderately tine to fine texture

low

low

low

Dclay soils, soils with high water table, shallow soils over impervious layer

very low

very low

very high

Group

Type


Leaching potential

Runoff potential


high

High

low


moderate

moderate

moderate


low

low

low


very low

very low

very high

Group

Type


Leaching potential

Runoff potential


high

High

low


moderate

moderate

moderate


low

low

low


very low

very low

very high

Hydrologic Group

Type Infiltration capacity/perm-

eability

Leaching potential

Runoff potential

A Deep, well drained sands and gravels

High High Low

B Moderately deep to deep, moderately

drained, moderate fine to moderately coarse

texture

Moderate Moderate Moderate

C Impeding layer, or moderately fine to fine

texture

Low Low High

D Clay soils, soils with high water table,

shallow soils over impervious layer

Very low Very low Very high

Soil Hydrologic Groups


• 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


• 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


• Soil capability class– Increase width of

zone 2 to provide combined width of zone 1 and 2 of,

Soil Capability Class

Buffer Width

Cap. I, II e/s, V 75 ft.

Cap. III e/s, IV e/s 100 ft.

Cap. VI e/s, VII e/s 150 ft.

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.

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).

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.

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

Indiana BMP RMZ Width Recommendations

Watercourse

Chara.

0-5% slope

5-10% slope

10-20% slope

20-40% slope

40% + slope

Primary RMZ

Perenial 40’ wide 200 200 200 200 200 200

Perenial 40 - 20’ wide

75 75 75 105 105-165 75

Perenial 20’ wide 50 50 65 105 105-165 35

Intermittent 25 45 65 105 105-165

Sinkhole openings

25 45 65 105 105-165

Water supply 75 90 130 210 210-300 75

Other lakes and ponds

35 45 65 105 105-165 35

Total RMZ Width*

* Width in feet on each side of watercourse

Midwest Issue

• Field drain tiles empty into drainage ditches that flow directly to waterways.

• Methods need to buffer tile water before it enters ditches.

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.

riparian forest buffers def. – land adjacent to a waterway is referred to as the “riparian...

Documents

restoration slide

drainage slide

goundwater slide

denitrification slide

water pollution

crop land slide

sediment filter sediment

forest floor sediment