Ecological impact assessment tools for fluvial flooding and coastal inundation

Old, Gareth; Acreman, Michael; Laize, Cedric; Nottage, Albert; Overton, Ian; Mountford, Owen; Packman, John; Walton, Sam; Cowx, Ian; Thorne, Colin; Thompson, Julian; Newman, Jonathan; Ramsbottom, David; Gouldby, Ben; Lumbroso, Darren; Gowing, David. 2010 Ecological impact assessment tools for fluvial flooding and coastal inundation. Environment Agency, 114pp. (CEH Project Number: C03429) (Unpublished)

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This report presents the scientific basis and development of the Ecological Impact Assessment (EIA) tools for fluvial flooding (EIA F tool) and coastal inundation (EIA C tool). These tools have been developed within the Ecological Consequences of Flooding (ECF) project and may be used to support an environmental risk assessment. When developing plans to manage flood risk, economic, social and environmental impacts are considered. There are many tools that help to estimate the economic impacts. However, there is currently no standard approach for evaluating the impacts on the natural environment within a flood risk assessment. Impacts of floods on the natural environment are often complex and include benefits and disbenefits. The Broad Scale Ecosystem Assessment (BSEA) toolkit is based on GIS data sets (existing or producible) that already exist or can be easily created and that have an apparent relationship with ecological characteristics. It is largely left to experts to interpret the ecological implications of these data. The project reported here builds on this work by introducing more scientific knowledge and objectivity to the assessment of ecological impact by developing prototype GIS based tools that will support decision making. The prototype tools developed here will be used to provide an initial assessment of ecological assets at risk of fluvial flooding and coastal inundation. In this way it will help all Flood and Coastal Risk Management (FCRM) authorites fulfil their duties under the EU Floods Directive, Habitats Directive, Bird’s Directive and Water Framework Directive. In the future it is envisioned that the tool will be embedded within software and made available to general users through an application like the Modelling Decision Support Framework that is used by the Environment Agency in the preparation of Catchment Flood Management Plans. The tools will thus support Environmental Impact Assessments and Strategic Environmental Assessments for flood risk management activities. The scoping study that underpins this project (Ramsbottom et al., 2005) concluded that although gaps exist in scientific understanding of ecological impacts and data coverage and resolution, it was feasible to integrate the available information within a Geographical Information System (GIS), and to produce prototype tools. Aim and Objectives The overall aim of the project is to develop, test and disseminate prototype methods for assessing and mapping the ecological risk, including harmful and beneficial effects, resulting from flooding. The aim was achieved through the following objectives. • Reviewing literature and consulting experts to identify current requirements, tools and knowledge • Defining the scope of the tool and ecologically significant hydrological indices • Deciding on the resolution of impact assessment • Specifying the methodology • Defining ecological sensitivities to flooding o Using scientific literature, empirical assessment and expert opinion • Preparing scorecards as frameworks for impact assessment • Producing guidance for the prototype tools • Pilot testing o Calibrating, verifying and assessing applicability of the proposed methods • Disseminating findings – including a scientific paper and good practice guidance. The prototype tools and their application The prototype tools described in this report guide the user in making an objective and quantitative (where appropriate) assessment of the ecological impact of floods on the environment using ARC GIS 9.3 with its standard toolbox supplemented with Spatial Analyst. Although GIS based, they are spreadsheet tools that assesses the ecological impact of a given hydrological scenario by comparing this to the sensitivities of mapped ecological assets. The tools would support anyone undertaking an ecological flood risk assessment. They represent a tiered approach (comparable to the BSEA) to ecological impact assessment which is necessary to ensure that an appropriate level of analysis is adopted which is justified by the importance of the decision. Step by step guidance in using the tools is available (Guidance Report). The ecological assessment is made using spreadsheet based scorecards. The ecological sensitivities defined above for impact assessment are captured on the scorecards. The user must define the current flooding/relative sea level rise scenario and undertake a series of defined spatial data queries before assessing the impacts of flooding. The user must specify the impact assessment criteria as these are likely to change with time and with the specific objectives of a given assessment (e.g. what is an allowable loss of bird habitat?). The impacts of flooding are then evaluated by comparing the sensitivities of flooding to the flood characteristics. Given that the prototype tools use many spatial datasets of varying resolution, accuracy, age and completeness several areas of uncertainty are identified and discussed. These must be acknowledged in any assessment and a decision must be made as to which need quantifying in a given study. The prototype tools have been tested in two fluvial and two coastal regions. Test of both tools were successful and demonstrated the applicability of the tools. A degree of verification was presented by expert assessment of the results of the pilot tests. Relevance to strategy and legislation The ECF method supports activities throughout the tiered approach to fluvial flood risk management planning. In particular, it supports catchment flood management planning, shoreline management planning, strategy planning and PFRAs (required under the Flood Risk Regulations 2009). The tools could also support the assessment of outcome measures, spatial planning and appraisal. They provide a framework for assessment although the level of detail would change from the high level CFMP/SMP to the more detailed Strategy Plan. The application of the tools at the more detailed scheme level requires further consideration and would need to include site specific information. The way the ECF tools link to existing tools and methods is considered as this is key to its successful integration to flood risk management. Conclusions and recommendations The prototype tools successfully integrate current scientific knowledge, expert opinion and available data in a framework that allows a more objective assessment of the ecological impacts of flooding. This was demonstrated through pilot testing. Our ability to assess the impacts of flooding on ecology would be greatly enhanced by the following: • Developing NAFRA data to include more ecologically relevant data (frequent floods, seasonality and duration) • Increasing coverage of up to date high resolution habitat mapping (e.g. National Vegetation Classification data) • Increasing scientific understanding of the sensitivities of environmental assets to flooding/inundation. The relevance of the methods to current strategy and legislation has been demonstrated by considering specific activities within flood risk management.

Item Type: Publication - Report (UNSPECIFIED)
Programmes: CEH Topics & Objectives 2009 onwards > Water > WA Topic 3 - Science for Water Management > WA - 3.4 - Develop novel and improved methods to enable the sustainable management of freshwaters and wetlands
CEH Sections: Acreman
Funders/Sponsors: Environment Agency
Additional Keywords: flooding, habitats, fish, sediment, birds
NORA Subject Terms: Management
Ecology and Environment
Date made live: 04 Nov 2011 12:18

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