Development of a Strategic-Level GIS Indicator-Based Watershed Assessment Procedure for Assessing Cumulative Watershed Effects

Doug Lewis – Resource Practices Specialist, BC Ministry of Forests, Lands and Natural Resource Operations, Kamloops, BCMichael Milne – Watershed Hydrologist, M.J. Mile & Associates Ltd., Vernon, BC.

Bill Grainger – Geoscientist, Grainger & Associates Ltd., Salmon Arm, BC.

1. Introduction and Background

5. Example: Private Land IndicatorIndicators are intended to broadly capture effects of land use activities. In this example, the potential impacts of riparian clearing on riparian function within private land are estimated by analysing the extent of streams that overlap with private land.

2. Risk-based Approach The procedure uses a risk-based approach where risk is a product of hazard and consequence defined by the risk equation (Risk = Hazard x Consequence) and as applied in the following matrix (Figure 2).

7. Indicator and Ratings Calibration To further refine preliminary estimates, independent measures of impacts, collected through targeted field-based monitoring in local catchments, are being used to calibrate indicator measures and associated hazard ratings. The results will be used to calibrate hazard ratings in subsequent versions and help validate model outcomes.

The procedure developed out of the need to understand potential cumulative watershed effects of land use activity and natural disturbance over broad geographic areas.

The procedure builds from existing watershed assessment procedures developed in BC (e.g. BC MOF 1999, Carver and Utzig 2000, Green 2005). The work is now used to support strategic-level cumulative effects assessment as part of BC’s Cumulative Effects Framework (Lewis et al. 2015).

The procedure is intended as a first step to flag ‘higher risk’ catchments as part of a multi-step watershed assessment approach (Figure 1).

6. Estimating Effects

3. Multi-Scale Reporting Structure We used BC Freshwater Atlas (FWA) 1:20,000 Watershed Assessment Unit (AU) boundaries (Carver and Gray, 2010) as the base units to build a hierarchical watershed structure for analysis and reporting hazard, consequence and risk ratings (Figure 3).

Fig 3. A.) Several large drainages (5th order or greater) that flow into the Thompson River west of Kamloops, BC in the Kamloops Assessment Area. B) The 6th order Deadman River Large Watershed. C) Watersheds within the Deadman River Large Watershed. D) Basins within the Criss Creek Watershed, southeast portion of Deadman River Large Watershed. E) Sub-basins and F) Residual Units within the Criss Creek watershed.

As a preliminary estimate of the likelihood of harmful changes in watershed processes, where possible we used quantitative synthesis of the response of watershed processes and/or aquatic organisms (benthic invertebrates, fish) to similar GIS-base metrics reported in the published literature.

4. GIS Indicators and Model Structure

Fig 4. Indicators used in the watershed assessment procedure illustrating the linkages to sensitivity, disturbance and hazard ratings used to express the likelihood of harmful changes in key watershed processes.

8. ConclusionsWe strongly recommend that further work is required to validate model outcomes, and adjust indicators, scores and hazard ratings accordingly. Nonetheless we have a high level of confidence that the indicators and their application in this method give a useful first approximation of the key hydrologic processes and watershed characteristics affecting streamflow, sediment and riparian function. Despite our confidence, we stress that GIS-based indicators should not be misused as management limits, but are intended to flag high risk catchments units for further investigation by qualified professionals as part of a multi-step approach referenced in Box 1.

9. Literature CitedB.C. Ministry of Forests, 1999. Watershed assessment procedure guidebook. 2nd ed. , Version 2.1. For. Prac. Br., Min. For, Victoria, BC. Forest Practices Code of British Columbia Guidebook. URL: http://www.for.gov.bc.ca/tasb/legsregs/fpc/FPCGUIDE/wap/WAPGdbk-Web.pdf Carver, M. 2001. Using Indicators to Assess Hydrologic Risk. Pages 26-43 In Toews, D.A.A., and S. Chatwin (editors). 2001. Watershed assessment in the southern interior of British Columbia. Res. Br., B.C. Min. For., Victoria, B.C. Work. Pap. 57/2001Carver, M and G, Utzig. 2000. A GIS-based hydrologic decision support tool for strategic planning in the Arrow Forest District. Unpublished report prepared for BC Ministry of Forests.Green, K. 2005. A qualitative hydro-geomorphic risk analysis for British Columbia’s interior watersheds: A discussion paper. Streamline watershed management Bulletin, Vol 8: No. 2. Lewis, D., Valdal, E., Milne, M.J., Grainger, B., and R. McCleary. 2015. the Application of a strategic-level watershed assessment procedure towards managing the unintended consequences of cumulative watershed effects in the southern interior of BC. Presentation this conference. Morley, S.A., and J.R. Karr. 2002. Assessing and restoring the health of urban streams in the Puget Sound basin. Cons. Biology 16(6): 1498-1509. Roth, N.E., Allan, J.D., and D.L. Erickson. 1996. Landscape influences on stream biotic integrity assessed at multiple spatial scales. Landscape ecology 11(30: 141-156. Tripp, D.B., P.J. Tschaplinski, S.A. Bird and D.L. Hogan. 2009. Protocol for Evaluating the Condition of Streams and Riparian Management Areas (Riparian Management Routine Effectiveness Evaluation). Forest and Range Evaluation Program, B.C. Min. For. Range and B.C. Min. Env., Victoria, BC.Wise, M., Moore, G., and D. Vandine. 2004. Definitions of terms and framework for landslide risk management. Chapter 2, pages 5-12 IN Wise, M.P., Moore, G.D., and D.F. Vandine. (editors). 2004. Landslide risk case studies in forest development planning and operations. B.C. Min. For., Res. Br., Victoria, B.C. land manage. Handb. No. 56. http://www.for.gov.bc.ca/hfd/pubs/Docs?Lmn?Lmh56.htm

AcknowledgmentsWe would like to thank a number of people for their assistance in the development of this procedure . Cam Brown of Forsite Consultants Ltd. provided initial work on GIS indicators. In earlier versions of the work upon which this procedure is built.. We are grateful to Sasha Lees and Graham MacGregor of BC MFLNRO for GIS support and indicator development and refinement. Martin Carver, Rita Winkler and Russell Smith provided useful insight and helpful comments through the development of earlier versions of this work. We would like to thank the Thompson Okanagan BC MFLNRO Integrated Monitoring Team for assistance in field-based assessments. We would also like to thanks David Huggard for statistical analysis of monitoring results and sampling support.

Fig. 2. Risk matrix used in watershed risk analysis (adapted from Wise et al., 2004)

Fig. 1. recommended multi-step approach to watershed analysis necessary to move from strategic-level recommendations to site-level actions

Fig 5. Example illustrations of private land clearing of riparian vegetation. Red lines indicate private land boundaries. Expanded illustrations show examples of residual riparian vegetation associated with private land logging or clearing for agriculture and urban development.

Fig 6. Quantitative synthesis of the relationship between percent agricultural (private) land and indices of biotic integrity from two published studies (Left). Synthesized results were used to estimate the likelihood of harmful changes to watershed processes (Right).

We used GIS-based indicators of inherent watershed sensitivity and land use activity/natural disturbance to three key watershed processes: streamflow, sedimentation and riparian function. Indicators were combined in ratings tables to provide sensitivity, disturbance and hazard ratings(Figure 4).

Fig 7. Targeted field-based assessments of stream functioning condition using BC’s Routine Riparian Effectiveness Evaluation protocol (Tripp, 2009) were compared with GIS-based Hazard ratings and showed strong relationships to both highest hazard and riparian hazard ratings (Left). We used Boosted Regression Tree (BRT)techniques to analyse the probability of properly functioning condition relative to indicator metrics . The percent of total watershed stream length adjacent (<30m)from harvesting showed the strongest relationship to stream functioning condition (Right).