An Overview of Mapping Riparian Zones: Issues and Possible Answers Ann L Maclean, Professor School of Forest Resources and Environmental Science Michigan Technological University Houghton, MI amaclean@mtu.edu Sinan Abood, Spatial Analyst Research Fellow USDA Forest Service Washington, DC sinanayadabood@fs.fed.us
http://publishing.cdlib.org/ucpressebooks/data/13030/wp/ft1c6003wp What is a Riparian Area (Zone, Buffer, Ecosystem)? Numerous definitions exist Vary with the perspective of the user Definitions depend on the what components of landscape are being focused on, landscape scale and legislative mandates for water quality best management practices (BMPs).
Common Components to the Numerous Definitions http://www.waternsw.com.au/waterquality/catchment/living/managing-land/riparian Adjacent to water (rivers, streams and lakes) Land inclusive of hydrophytes Soil saturated by ground water for at least part of the growing, thus including wetlands and adjacent lands with a moderate or well balanced supply of moisture Part of the floodplain
en.wikipedia.org Historically riparian zones have been mapped using fixed width buffers. Viewed as primarily as protection zones against sedimentation and nutrient runoff. Easy to delineate. Limitation- only consider moving watercourse.
BMP s dictate width of buffers. Differ dramatically from state to state. Watershed boundaries seldom follow political boundaries. From: Mason, 2007
Fixed width buffers don t emulate natural riparian corridors since have no functional relationship to natural varying watercourse. www.ridgedalepermaculture.com Important to consider surrounding geomorphology and associated vegetation. Past research has shown that on average, actual riparian zone boundary may be 2.5 time farther from the watercourse than protected by a fixed width buffer (Skally and Sagor, 2001).
http://www8.garmin.com/graphics/24sat ellite.jpg www.fortmillcarecenter.org
How Improve Modeling and Mapping Riparian Zones? Ideal model would be: Easy to use Generate a variable width buffer Scale independent http://ian.umces.edu/imagelibrary/albums/userpics/844 69/normal_iil_eco_af_0018.jpg Consider surrounding geomorphology and vegetation Independent of land form & related ecosystems No subjective interpreted inputs Applicable to a wide array of applications Accurate output Model inputs widely available, high quality geospatial data: DEMs, stream gauge data, soils and vegetation, including wetlands
Numerous models have been developed. Most require subjective input which introduces a random error that can t be modeled or ignore critical components of a riparian zone. Examples include Manual delineation of vegetation types (Triepke et al, 2013) Manual delineation of riparian areas via valley types classification (Holmes and Goebel, 2011) Various methodologies for calculating wetness indexes- (Triepke et al, 2013) Exclusion of intermittent & ephemeral streams in the mapping process Use of coarse spatial resolution & integer format DEMs Inaccurate flood height calculation
Hydrologic Flood Height Calculation Research by Ilhardt et al. (2000) determined 50 year flood plain as optimal hydrologic descriptor for riparian zones. This height, in most cases, intersects the first terrace or other upward sloping surface and supports same microclimate and geomorphology as stream channel. 50 year flood plain also coincides with measurements that quantify a valley to its stream via 2 measurements: entrenchment ratio (valley width at first terrace or up slope to the stream width at full bank) and the belt width ratio.
Calculate the 50-year floodplain using the Hydrologic Estimation.xlsm file developed according to Mason (2007) and Bedient & Huber (2002).
Flood Height Calculation from Multiple Gauges by Stream Order 5.00 4.50 Average 50 yfh y = 0.0264x 3-0.2319x 2 + 0.6234x - 0.2212 R² = 0.9039 4.00 3.50 50 YAER FLOODPLAN 3.00 2.50 2.00 1.50 1.00 0.50 0.00 0 1 2 3 4 5 6 7 8 9 STREAMS ORDER Average 50 yfh Poly. (Average 50 yfh)
DEM Spatial Resolution DEM spatial resolution and data format impact area of riparian zone. Accuracy assessment of zones mapped from 30m vs 10m area are statistically different (p<0.001). Finer spatial resolution DEMs increases accuracy of boundary location. 1m DEM 3m DEM 5m DEM 10m DEM RB Area 6,176.7 7,328.1 7,550.0 8,366.8 % watershed 7.65 9.07 9.35 10.36 From: Abood, 2010
Intermittent and ephemeral streams- mapping is important particularly in arid regions
References Abood, S.A., 2011. Modeling and Classifying Variable Width Riparian Zones Utilizing Digital Elevation Models, Flood Height Data, Digital Soil Data and National Wetlands Inventory: A New Approach for Riparian Zone Delineation, Ph.D. Dissertation, Michigan Technological University, Houghton, Michigan, 111 p. Abood, S.A., Maclean A.L., Mason L.A., 2012, Modeling Riparian Zones Utilizing DEMs and Flood Height Data via GIS. Photogrammetric Engineering and Remote Sensing. 78(3):259-269. Bedient, P.B and W.C. Huber. 2002. Hydrology and Floodplain Analysis, 3 rd edition. Prentic Hall, 763 p. Holmes, K.L. and P.C. Goebel. 2011. A Functional Approach to Riparian Delineation Using Geospatial Methods. Journal of Forestry. 233-241. Ilhardt, B.L., E.S. Verry and B.J. Palik. 2000. Defining Riparian Areas. Riparian Management in Forests of the Continental Eastern United States. (Verry, E.S., J.W. Hornbeck and C.A. Dolloff, editors). Lewis Publishers, New York., NY, pp. 23-42. Mason, L., 2007. GIS Modeling of Riparian Zones Utilizing Digital Elevation Models and Flood Height Data, M.S. Thesis, Michigan Technological University, Houghton, Michigan, 75 p.
Triepke, F.J., M.M Wahlberg, D.C Cress, and R.L. Benton. 2013. RMAP Regional Riparian Mapping Project. USDA Forest Service project report available online http://fs.usda.gov/main/r3/landmanagement/gis. Southwestern Region, Albuquerque, NM. 53 pp. Skally, C., and E. Sagor, 2001. Comparing riparian management zones to riparian areas in Minnesota: A pilot study, Research Report RR-1001, Minnesota Forest Resources Council, St. Paul, Minnesota, 11 p. Verry, E.S., C.A. Dolloff and M.E. Manning. 2004. Riparian ecotone: a functional definition and delineation for resource assessment, Water, Air, and Soil Pollution: Focus 4:67-94.