Markus Schnorbus

Forests and floods: A new paradigm sheds light on age‐old controversies

[1] The science of forests and floods is embroiled in conflict and is in urgent need of reevaluation in light of changing climates, insect epidemics, logging, and deforestation worldwide. Here we show how an inappropriate pairing of floods by meteorological input in analysis of covariance (ANCOVA) and analysis of variance (ANOVA), statistical tests used extensively for evaluating the effects of forest harvesting on floods smaller and larger than an average event, leads to incorrect estimates of changes in flood magnitude because neither the tests nor the pairing account for changes in flood frequency. We also illustrate how ANCOVA and ANOVA, originally designed for detecting changes in means, do not account for any forest harvesting induced change in variance and its critical effects on the frequency and magnitude of larger floods. The outcomes of numerous studies, which applied ANCOVA and ANOVA inappropriately, are based on logical fallacies and have contributed to an ever widening disparity between science, public perception, and often land-management policies for decades. We demonstrate how only an approach that pairs floods by similar frequency, well established in other disciplines, can evaluate the effects of forest harvesting on the inextricably linked magnitude and frequency of floods. We call for a reevaluation of past studies and the century-old, preconceived, and indefensible paradigm that shaped our scientific perception of the relation between forests, floods, and the biophysical environment.

Uncertainties in Hydrologic and Climate Change Impact Analyses in Headwater Basins of British Columbia

AbstractThree headwater basins located across British Columbia (BC) were analyzed using a hydrologic model driven by five global climate models (GCMs) and three scenarios from the Special Report on Emissions Scenarios (SRES) to project future changes in seasonal water budgets and assess the uncertainty in the projections arising from GCMs, emissions scenarios, and hydrologic model parameterizations under two future time periods. Future projected changes in temperature are for annual increases of approximately +2°C by the 2050s and +3°C by the 2080s. The 2050s and 2080s precipitation projections are for increased winter precipitation in all basins and decreases in summertime precipitation for two of the three basins—with increases projected in the northeastern BC subwatershed. The study found that the hydrologic parameter uncertainty ranged up to 55%, (average 31%) for winter runoff anomalies, which was less than the uncertainty associated with GCMs and emissions scenarios that ranged up to 135% and 78% (a...

Evaluating Hydroclimatic Change Signals from Statistically and Dynamically Downscaled GCMs and Hydrologic Models

AbstractThis study analyzed potential hydroclimatic change in the Peace River basin in the province of British Columbia, Canada, based on two structurally different approaches: (i) statistically downscaled global climate models (GCMs) using the bias-corrected spatial disaggregation (BCSD) and (ii) dynamically downscaled GCM with the Canadian Regional Climate Model (CRCM). Additionally, simulated hydrologic changes from the GCM–BCSD-driven Variable Infiltration Capacity (VIC) model were compared to the CRCM integrated Canadian Land Surface Scheme (CLASS) output. The results show good agreements of the GCM–BCSD–VIC simulated precipitation, temperature, and runoff with observations, while the CRCM-simulated results differ substantially from observations. Nevertheless, differences (between the 2050s and 1970s) obtained from the two approaches are qualitatively similar for precipitation and temperature, although they are substantially different for snow water equivalent and runoff. The results obtained from th...

Generation of an Hourly Meteorological Time Series for an Alpine Basin in British Columbia for Use in Numerical Hydrologic Modeling

Abstract Spatially distributed numerical hydrologic models are useful tools for examining the long-term impact of forest harvesting in mountainous basins on streamflow regime properties. Such models require the input of long-duration subdaily meteorological time series data that are not routinely available in mountainous headwater basins. A relatively simple method is presented for extending short-duration records by using a combined stochastic–empirical technique, and the approach is demonstrated using the Redfish Creek in British Columbia, Canada. Synthetic hourly precipitation, precipitation gradient, air temperature, temperature lapse rate, wind speed, relative humidity, solar beam and diffuse irradiance, and downward longwave irradiance for two station locations are generated in a three-step process: 1) hourly precipitation is generated using a clustered rectangular pulse point process, 2) daily meteorology is generated using a multivariate first-order autoregressive process, and 3) final hourly nonp...

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H12A-06. Brooks, K. N., P. F. Ffolliott, H. M. Gregersen, and L. F. DeBano (2003), Hydrology and the Management of Watersheds, Blackwell, Ames, Iowa. Bruijnzeel, L. A. (1990), Hydrology of Moist Tropical Forests and Effects of Conversion: A State of Knowledge Review, Div. of Water Sci., U.N. Educ., Sci., and Cult. Organ., Paris. Bruijnzeel, L. A. (2004), Hydrological functions of tropical forests: Not seeing the soil for the trees?, Agric. Ecosyst. Environ., 104, 185–228, doi:10.1016/j.agee.2004.01.015. Bruijnzeel, L. A. (2005), Land use and land cover effects on runoff processes: Forest harvesting and road construction, in Encyclopedia of Hydrological Sciences, edited by M. G. Anderson, chap. 119, pp. 1813–1830, John Wiley, Hoboken, N. J. Burnham, K. P., and D. R. Anderson (2002), Model Selection and Multimodal Inference: A Practical Information-Theoretic Approach, 2nd ed., Springer, New York. Burt, T. P., andW. T. Swank (1992), Flow frequency responses to hardwoodto-grass conversion and subsequent succession, Hydrol. Processes, 6, 179–188, doi:10.1002/hyp.3360060206. Caissie, D., S. Jolicoeur, M. Bouchard, and E. Poncet (2002), Comparison of streamflow between pre and post timber harvesting in Catamaran Brook (Canada), J. Hydrol., 258, 232 – 248, doi:10.1016/S00221694(01)00576-5. Calder, I. R. (2002), Forest and hydrological services: Reconciling public and science perceptions, Land Use Water Resour. Res., 2, 1–12. Calder, I. R. (2004), Forests and water—Closing the gap between public and science perceptions, Water Sci. Technol., 49, 39–53. Calder, I. R. (2005), Blue Revolution: Integrated Land and Water Resource Management, Earthscan, London. Calder, I. R., and B. Aylward (2006), Forest and floods: Moving to an evidence-based approach to watershed and integrated flood management, Int. Water Resour. Assoc., 31, 1–13. Calder, I. R., et al. (2004), Forest and water policies: The need to reconcile public and science perceptions, Geol. Acta, 2, 157–166. Calder, I. R., J. Smyle, and B. Aylward (2007), Debate over flood-proofing effects of planting forests, Nature, 450, 945, doi:10.1038/450945b. Chang, M. (2006), Forest and streamflow, in Forest Hydrology: An Introduction to Water and Forests, chap. 10, pp. 191–236, CRC Press, Boca Raton, Fla. Cheng, J. D. (1989), Streamflow changes after clear-cut logging of a pine beetle-infested watershed in southern British Columbia, Canada, Water Resour. Res., 25, 449–456, doi:10.1029/WR025i003p00449. Cohen, J. (1994), The earth is round (p < .05), Am. Psychol., 45, 1304– 1312, doi:10.1037/0003-066X.45.12.1304. Cohen, J., and I. Stewart (1994), The Collapse of Chaos: Discovering Simplicity in a Complex World, Penguin, New York. Cuo, L., D. P. Lettenmaier, M. Alberti, and J. E. Richey (2009), Effects of a century of land cover and climate change on the hydrology of the Puget Sound basin, Hydrol. Processes, 23, 907 –933, doi:10.1002/ hyp.7228. DeFries, R., and K. N. Eshleman (2004), Land-use change and hydrologic processes: A major focus for the future, Hydrol. Processes, 18, 2183– 2186, doi:10.1002/hyp.5584. DeWalle, D. R. (2003), Forest hydrology revisited, Hydrol. Processes, 17, 1255–1256, doi:10.1002/hyp.5115. Dhakal, A. S., and R. Sidle (2004), Pore water pressure assessment in a forested watershed: Simulations and distributed field measurements related to forest practices, Water Resour. Res., 40, W02405, doi:10.1029/ 2003WR002017. Dhakal, A. S., and R. Sidle (2008), Discussion on ‘‘Ground-water response to forest harvesting: Implications for hillslope stability’’ by Johnson, A. C., Edwards, R. T. and Erhardt, R, J. Am. Water Resour. Assoc., 44, 1–7, doi:10.1111/j.1752-1688.2008.00168.x. Draper, N. R., and H. Smith (1998), Applied Regression Analysis, John Wiley, New York. Dunne, T. (1998), Critical data requirements for prediction of erosion and sedimentation in mountain drainage basins, J. Am. Water Resour. Assoc., 34, 795–808, doi:10.1111/j.1752-1688.1998.tb01516.x. Dyrness, C. T. (1969), Hydrologic properties of soils on three small watersheds in the western Cascades of Oregon, Res. Notes PNW-111, For. Serv., U.S. Dep. of Agric., Corvallis, Oreg. Eaton, B., and M. Church (2001), Hydrological effects of forest harvest in the Pacific Northwest, Riparian Decis. Tool Tech. Rep. 3, 56 pp., Dep. of Geogr., Univ. of B. C., Vancouver, B. C., Canada. Eisenbies, M. H., W. M. Aust, J. A. Burger, and M. B. Adams (2007), Forest operations, extreme events, and considerations for hydrologic modeling in the Appalachians—A review, For. Ecol. Manage., 242, 77–98, doi:10.1016/j.foreco.2007.01.051. El Adlouni, S., T. B. M. J. Ouarda, X. Zhang, R. Roy, and B. Bobée (2007), Generalized maximum likelihood estimators for the nonstationary generalized extreme value model, Water Resour. Res., 43, W03410, doi:10.1029/2005WR004545. Elder, K., L. Porth, and C. A. Troendle (2006), The effect of timber harvest on the Fool Creek watershed after five decades, Eos Trans. AGU, 87(52), Fall Meet. Suppl., Abstract B21F-01. Elliott, L. P., and B. W. Brook (2007), Revisiting Chamberlain: Multiple working hypotheses for the 21st Century, BioScience, 57, 608–614, doi:10.1641/B570708. Folland, C., and C. Anderson (2002), Estimating changing extremes using empirical ranking methods, J. Clim., 15, 2954–2960, doi:10.1175/15200442(2002)015<2954:ECEUER>2.0.CO;2. Food and Agriculture Organization of the United Nations (FAO) (2003), The State of the World’s Forests, Rome. Food and Agriculture Organization of the United Nations/Center for International Forestry Research (FAO/CIFOR) (2005), Forests and Floods: Drowning in Fiction or Thriving on Facts?, Bangkok. Forsyth, T. (2005), Land use impacts on water resources—Science, social and political factors, in Encyclopedia of Hydrological Sciences, edited by M. G. Anderson, chap. 187, pp. 2911–2924, John Wiley, Hoboken, N. J. Gilmour, D. A., M. Bonell, and D. S. Cassells (1987), The effects of forestation on soil hydraulic properties in the Middle Hills of Nepal: A preliminary assessment, Mt. Res. Dev., 7, 239 – 249, doi:10.2307/ 3673199. Goodell, B. C. (1958), A preliminary report on the first year’s effects of timber harvesting on water yield from a Colorado watershed, Pap. 36, Rocky Mt. For. and Range Exp. Stn., For. Serv., U.S. Dep. of Agric., Fort Collins., Colo. Grant, G. E., S. L. Lewis, F. J. Swanson, J. H. Cissel, and J. J. McDonnell (2008), Effects of forest practices on peak flows and consequent channel response: A state-of-science report for western Oregon and Washington, Gen. Tech. Rep. PNW-GTR-760, Pac. Northwest Res., Stn., U.S. Dep. of Agric., Portland, Oreg. Gucinski, H., and M. Furniss (2000), Forest roads: A synthesis of scientific information, For. Serv., U.S. Dep. of Agric., Washington, D. C. (Available at www.fs.fed.us/news/roads/science.pdf) Guillemette, F., A. P. Plamondon, M. Prevost, and D. Levesque (2005), Rainfall generated stormflow response to clearcutting a boreal forest: Peak flow comparison with 50 worldwide basin studies, J. Hydrol., 302, 137–153, doi:10.1016/j.jhydrol.2004.06.043. Guthery, F. S., J. J. Lusk, and M. J. Peterson (2001), The fall of the null hypothesis: Liabilities and opportunities, J. Wildl. Manage., 65, 379– 384, doi:10.2307/3803089. W08416 ALILA ET AL.: FORESTS AND FLOODS—A NEW PARADIGM

Statistical emulation of streamflow projections from a distributed hydrological model: Application to CMIP3 and CMIP5 climate projections for British Columbia, Canada

A recent hydrological impacts study in British Columbia, Canada, used an ensemble of 23 climate change simulations to assess potential future changes in streamflow. These Coupled Model Intercomparison Project Phase 3 (CMIP3) simulations were statistically downscaled and used to drive the Variable Infiltration Capacity (VIC) hydrology model over several watersheds. Due to computational restrictions, the 23 member VIC ensemble is a subset of the full 136 member CMIP3 archive. Extending the VIC ensemble to cover the full range of uncertainty represented by CMIP3, and incorporating the latest generation CMIP5 ensembles, poses a considerable computing challenge. Thus, we extend the VIC ensemble using a computationally efficient statistical emulation model, which approximates the combined output of the two-step process of statistical downscaling and hydrologic modeling, trained with the 23 member VIC ensemble. Regularized multiple linear regression links projected changes in monthly temperature and precipitation with projected changes in monthly streamflow over the Fraser and Peace River watersheds. Following validation, the statistical emulator is forced with the full suite of CMIP3 and CMIP5 climate change projections. The 23 member VIC ensemble has a smaller spread than the full ensemble; however, both ensembles provide the same consensus estimate of monthly streamflow change. Qualitatively, CMIP5 shows a similar streamflow response as CMIP3 for snow-dominated hydrologic regimes. However, by end-century, the CMIP5 worst-case RCP8.5 has a larger impact than CMIP3 A2. This work also underscores the advantage of using emulation to rapidly identify those future extreme projections that may merit further study using more computationally demanding process-based methods.

A Dynamical Climate Model–Driven Hydrologic Prediction System for the Fraser River, Canada

AbstractRecent improvements in forecast skill of the climate system by dynamical climate models could lead to improvements in seasonal streamflow predictions. This study evaluates the hydrologic prediction skill of a dynamical climate model–driven hydrologic prediction system (CM-HPS), based on an ensemble of statistically downscaled outputs from the Canadian Seasonal to Interannual Prediction System (CanSIPS). For comparison, historical and future climate traces–driven ensemble streamflow prediction (ESP) was employed. The Variable Infiltration Capacity model (VIC) hydrologic model setup for the Fraser River basin, British Columbia, Canada, was used as a test bed for the two systems. In both cases, results revealed limited precipitation prediction skill. For streamflow prediction, the ESP approach has very limited or no correlation skill beyond the months influenced by initial hydrologic conditions, while the CM-HPS has moderately better correlation skill, attributable to the enhanced temperature predict...

Projecting future nonstationary extreme streamflow for the Fraser River, Canada

We describe an efficient and flexible statistical modeling framework for projecting nonstationary streamflow extremes for the Fraser River basin in Canada, which is dominated by nival flow regime. The framework is based on an extreme value analysis technique that allows for nonstationarity in annual extreme streamflow by relating it to antecedent winter and spring precipitation and temperature. We used a representative suite of existing Variable Infiltration Capacity hydrologic model simulations driven by Coupled Model Intercomparison Project Phase 3 (CMIP3) climate simulations to train and evaluate a nonlinear and nonstationary extreme value model of annual extreme streamflow. The model was subsequently used to project changes under CMIP5-based climate change scenarios. Using this combination of process-based and statistical modeling, we project that the moderate (e.g., 2–20-year return period) extreme streamflow events will decrease in intensity. In contrast, projections of high intensity events (e.g., 100–200-year return period), which reflect complex interactions between temperature and precipitation changes, are inconclusive. The results provide a basis for developing a general understanding of the future streamflow extremes changes in nival basins and through careful consideration and adoption of appropriate covariates, the methodology could be employed for basins spanning a range of hydro-climatological regimes.

Improving gridded snow water equivalent products in British Columbia, Canada: multi-source data fusion by neural network models

Estimates of surface snow water equivalent (SWE) in mixed alpine environments with seasonal melts are particularly difficult in areas of high vegetation density, topographic relief, and snow accumulations. These three confounding factors dominate much of the province of British Columbia (BC), Canada. An artificial neural network (ANN) was created using as predictors six gridded SWE products previously evaluated for BC. Relevant spatiotemporal covariates were also included as predictors, and observations from manual snow surveys at stations located throughout BC were used as target data. Mean absolute errors (MAEs) and interannual correlations for April surveys were found using crossvalidation. The ANN using the three best-performing SWE products (ANN3) had the lowest mean station MAE across the province. ANN3 outperformed each product as well as product means and multiple linear regression (MLR) models in all of BC’s five physiographic regions except for the BC Plains. Subsequent comparisons with predictions generated by the Variable Infiltration Capacity (VIC) hydrologic model found ANN3 to better estimate SWE over the VIC domain and within most regions. The superior performance of ANN3 over the individual products, product means, MLR, and VIC was found to be statistically significant across the province.