Stream Buffer: Kidneys of the Watershed?

Transcription

1 2012 A. D. Latornell Conservation Symposium Stream Buffer: Kidneys of the Watershed? John E. FitzGibbon Professor of Planning University of Guelph

2 Definition a complex assemblage of plants and other organisms in an environment adjacent to water. Without definitive boundaries, it may include stream banks, floodplain, and wetlands, as well as sub-irrigated sites forming a transitional zone between upland and aquatic habitat. Mainly linear in shape and extent, they are characterized by laterally flowing water that rises and falls at least once within a growing season.( Lowrance, Leonard, and Sherida, 1985)

3 Types of Flow Runoff Processes: Simple Cross section Source: Modified from Bernier and Bernier 1987

4 Runoff Processes: Complex 3 D View Source: E.T. Engman, June 1974

5 Runoff Processes: Simple Plan Form Source E. Engman, 1974

6 Changes in Runoff Producing Areas Very Dry watershed Dry Watershed Wet Watershed Very Wet Watershed Source : After Hewlett and Nutter 1970

7 Functions of Stream Buffers 1) They can alter runoff (low flow) 2) They functions as filters for surface runoff 3) They function as filters for shallow sub surface flow 4) They function as sources of organic material 5) They can reduce stream temperature 6) They function as places of habitat for some creatures

8 Buffer Removal of Phosphorous

9 Buffer Nitrate removal for Riparian Buffers of different widths and vegetation cover

10 Nitrogen Pathways in Riparian Buffers

11 The Three Zone Approach (USDA) Functions Features Source : USDA

12 Characteristics to Consider Topography/ geomorphology/slope/ location Soil Type Adjacent land use implication e.g. Land management Species and plant community structure Drainage processes e.g. Surface subsurface, saturated overland, depth to water table at critical times Activities in the riparian buffer zone e.g. Harvesting trafficking etc.

13 Source: Ian MacDonald, OMAFRA 2009 Concentrated Overland Flow

14 Risk Factors Increased risk : Occurs on Long Slopes Occurs in areas where there is a convergence of slope Occurs along lines of saturated soil or impermeable soil Occurs where the shear strength of the soil is unable to resist the force of the water (non vegetated, changes to steep slope angle)

15 Response to Concentrated Overland Flow Change tillage practice contour ploughing and cropping. Tile drainage with surface inlets. Implement grassed water ways. Terracing Full Permanent cover (pasture)

16 Grassed Water Way Source: Agriculture Canada

17 Enhanced Grassed Water Ways Source: NCRS, USDA

18 Integrated System of Erosion Management Source: Jane Thomas, IAN Image Library University of Maryland, Centre for Environmental Sciences

19 Experimental System of Buffers

20 No Free Lunch (Buffer Maintenance) Buffers can become saturated with sediment, phosphorous and can loose their efficacy at with Nitrogen removal. Buffers should periodically be renewed through ploughing and crop removal removes nutrients and prevent contamination especially for phosphorous. Mowing of grassed buffers assists with increasing grasses densities by encouraging tillering. Reduced trafficking increases the infiltration of water into buffers that are not saturated. Managed harvesting of standing bio-mass can reduce flooding erosion by overbank flows and helps maintain channel integrity

21 Major Impediments to buffers and integrated rural runoff management Loss of productive land Interference with land use (trafficking) Potential for increased flooding due to woody debris in channels Costs of establishment Costs and responsibility for maintenance Increased crop damage from wild life Management of invasive species Impacts on predatory species