An Approach for Developing Regional Environmental Benefits Models

OVERVIEW: Ecosystem restoration projects in a given region often have similar drivers, stressors, state conditions, and ecosystem services. Moreover, objectives and accompanying metrics may be similar enough to encourage regional model development. Regional approaches to environmental benefits analysis offer opportunities to streamline project evaluation by developing consistent understanding, metrics, and models. This technical note proposes a framework for developing regionally applicable environmental benefits models. The proposed framework is demonstrated for streams in the Appalachian Piedmont. This approach could serve as a basis for developing consistent restoration outputs that can be combined and compared at regional scales. INTRODUCTION: Owing to the complexity and variability of natural systems, accounting for the benefits of ecosystem restoration, management, and mitigation efforts with scientifically based, repeatable, and transparent techniques can be challenging (Fischenich et al. in preparation). To overcome these obstacles, models of environmental effects have been developed in regions with similar hydrologic, geomorphic, and ecological processes (e.g., ecoregions or physiographic provinces). Some commonly applied regional models of environmental benefit and impact include indices of biotic integrity (Karr 1991, Smogor and Angermeier 2001, Georgia Department of Natural Resources ((GA-DNR) 2005), wetland assessments with hydrogeomorphic methods (Brinson 1993, Smith et al. 1995, Brinson and Rheinhardt 1996), and regional environmental flow standards (Poff et al. 2010, Snelder et al. 2011). Herein, these regional approaches are augmented with standard methods for conceptual and numerical model development. The result of this combined approach is a framework for developing regionally applicable models of environmental benefits. Although regional models have been developed for varying purposes (e.g., impact assessment, mitigation requirements), the focus of this technical note is on the regional approach as it pertains to the evaluation of proposed ecosystem restoration projects. The regional modeling approach outlined here may help USACE planners develop scientifically based models of environmental benefits and construct model documentation capable of addressing rigorous quality assurance standards typically highlighted during various internal and external peer review processes. WHY DEVELOP A REGIONAL MODEL? Prior to examining the framework for regional model development, it is constructive to review strengths and weaknesses of regional models. The primary advantages of developing a regional model include: 1