Chap. 1 Introduction


Chapter Summary

Since their earliest settlements, humans have experimented with and adopted ways to manage flood risk. Some approaches are designed to prevent, some to manage, and others to handle the impact of floods. Anyone exploring flood risk management options should understand how different methods are intended to work - and under which circumstances. The financial, social and environmental costs and benefits of various flood management interventions also should be examined.

When communities live, work and play in areas prone to flooding, they expose themselves to flood-related damage. [1] Human activity (such as landfill, damming and urbanization) can introduce new risks to areas previously not subjected to flooding. In both cases, flood risk can be managed by altering either the natural or physical features (such as landscape, hydraulics, vegetation) or human activities (such as land use plans and settlement locations).

The Natural and Nature-Based Flood Management: A Green Guide (Flood Green Guide) supports the concept that flood risk management measures should be comprehensive, locally specific, integrated and balanced across all concerned sectors. [2] Therefore, the guide is based to the extent possible and practical on the integrated flood management (IFM) approach as defined by the Associated Programme on Flood Management (APFM):

"IFM integrates land and water resources development in a river basin, within the context of integrated water resources management, with a view to maximizing the efficient use of floodplains and to minimizing loss of life and property. Integrated flood management, like integrated water resources management, should encourage the participation of users, planners and policymakers at all levels. The approach should be open, transparent, inclusive and communicative; should require the decentralization of decision-making; and should include public consultation and the involvement of stakeholders in planning and implementation." [3]

For the purpose of the Flood Green Guide, we use the definitions adopted by the US Army Corps of Engineers (USACE) to describe natural features as those created through the action of physical, biological, geologic, and chemical processes operating in nature, whereas nature-based features are created by human design, engineering and construction. [4] Throughout the guide, we use the terms "natural" and "nature-based" interchangeably. We also recognize that in some cases, practitioners may use other terms, such as "green" or "green infrastructure," interchangeably with the terms natural and nature-based.

The Flood Green Guide organizes flood management methods into two categories: structural and non-structural. Structural methods involve physical changes to natural features or human infrastructure, including engineered (hard) methods (sometimes referred to as gray methods), such as dams or floodways, and natural and nature-based (soft) methods (sometimes referred to as green methods), such as wetland protection, upper watershed restoration or rain gardens.

Non-structural measures are defined as those that seek to change social conventions like laws, regulations, social institutions, organizations or individual behavior. Most flood risk management projects will comprise both structural (hard and soft methods) and non-structural components. In the Flood Green Guide, we recommend the use of a combination of multiple methods of hard and soft, structural and non-structural approaches that complement one another and enhance the efficacy of any existing flood risk management methods. In most cases, a combination of methods will be required and, therefore, the use of a single approach in isolation is not advised. Chapter 5 of the guide discusses in detail a comprehensive list of structural and non-structural flood risk management methods.

The "How to Use the Flood Green Guide" chapter leads those responsible for flood management (referred to as managers or guide users) through information gathering, analysis, and decision-making at multiple stages of a typical flood risk management project cycle. [5]



[1] The Flood Green Guide recognizes the definition of a community can vary and is context specific.

[2] Abhas K. Jha, Robin Bloch and Jessica Lamond, Cities and Flooding: A Guide to Integrated Urban Flood Risk Management for the 21st Century (Washington, DC: World Bank Publications, 2012), 167.

[3] Associated Programme for Flood Management (APFM) and World Meteorological Organization (WMO), Integrated Flood Management: Concept Paper, Integrated Flood Management Tools, no. 1047 (Geneva, Switzerland: WMO, 2009).

[4] US Army Corps of Engineers (USACE), Coastal Risk Reduction and Resilience (Washington, DC: Directorate of Civil Works, 2013).

[5] Although the Flood Green Guide was written to address most types of floods, glacial lake outburst floods (GLOFs) are not discussed in this document.

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