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Benefit Indicators for Flood Regulation Services of Wetlands: A Modeling Approach
Bousquin, J., K. Hychka, AND M. Mazzotta. Benefit Indicators for Flood Regulation Services of Wetlands: A Modeling Approach. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-15/191, 2015.
This project is developing approaches to assess and communicate the benefits of ecological restoration in urbanizing areas. Using the Woonasquatucket Watershed as a proof of concept study area, we developed indicators of benefits to people from the flood regulation services of wetlands, to inform and facilitate restoration decisions in a watershed.
This report describes a method for developing indicators of the benefits of flood regulation services of wetlands and presents a companion case study. We demonstrate our approach through an application to the Woonasquatucket River watershed in northern Rhode Island. This work is intended to address an important component of the assessment of ecosystem services: the development of metrics that clearly show how ecosystem functioning benefits people. What is unique and most useful about the approach presented here is that it incorporates people and the benefits they receive from ecosystem restoration assessment. Further, it provides a framework that can be used to compare potential wetland restoration scenarios based on these benefits without the need for estimating dollar values. This approach contributes in three ways to the assessment of flood regulation services provided by wetlands. First, it goes beyond standard ecological assessments of wetlands functioning by linking functioning with how, where, and how many people benefit from wetlands. Second, it provides a means of estimating defensible metrics using a tiered approach ranging from metrics that are more easily estimated but with greater uncertainty, to metrics that require detailed modeling and provide reduced uncertainty. Third, it works as an add-on to existing functional assessment tools, in order to extend their applicability to assessing ecosystem services, or augments economic benefit transfer approaches by providing metrics that can be used to determine the “extent of the market” for flood reduction benefits or to adjust values to better reflect local conditions.The benefits indicators approach developed in this report attempts to provide decision makers with a more accessible alternative to monetary valuation, and with an approach that explicitly links functions to benefits. We propose criteria to facilitate comparison of freshwater wetland restoration scenarios based not only on production of ecosystem services, but also on how those services reach and benefit people. The purpose of the indicators we present here is to provide metrics of the factors that influence the spatial flow of services from production to benefits, by assessing how flood waters flow across the geographic area between wetlands that retain or slow storm water flows and the important structures and other resources that might be protected from flood risks. We based indicators on sophisticated flood modeling results to ensure the rigor of results, but we recognize that in some contexts a rapid assessment that can be readily applied to inform a decision may be more valuable than a complex approach that is not feasible to apply. In an attempt to satisfy the requirements of different decision contexts, we created a 3-tiered approach. Based on the appropriate level of rigor for the decision context, each tier becomes more resource intensive to implement and requires more specific data. To apply the Tier III approach, an end user would need to perform extensive modeling similar to that described here, which is often too resource intensive and technical for most decision makers and many decision contexts. Tier II indicators were developed from trends and sensitivity observed in our modeling results. The correlation between Tier II results and the model outputs, as well as their basis in economic theory, allow for relatively high confidence in their defensibility, at least for watersheds similar in hydrological characteristics to our case study watershed. Tier I indicators are expected to be the least robust but most accessible. These indicators were not derived from model outputs, but are taken from the literature. We do not present Tier I indicators in this report, but they are included in a separate guide for decision makers, which presents the overall benefit indicators approach and provides a spreadsheet tool for applying Tier I indicators.