 Rainfall of Eastern United States, technical report, part V (Dayton, Ohio, 1917).
21 J. A. A. Jones, Global Hydrology: Processes, Resources and Environmental Management (Essex, England, 1997), 102; Miami Conservancy District, Storm Rainfall of Eastern United States (Revised), technical reports, part V (Dayton, Ohio, 1936), 105.
23 Report of the Federal Civil Works Program as Administered by the Corps of Engineers, Annual Report of the Chief of Engineers, part 1, vol 3 (1951): 404.
Grant, "The Probability-Viewpoint in Hydrology," 8.
Wisler and Brater, Hydrology, 4-5.
The susceptibility of land to flooding is a planning consideration; The Federal Environment Agency has the lead role in providing advice on flood issues, at a strategic level and in relation to planning applications; Development plans should give consideration to flood issues in light of uncertainties inherent in the prediction of flooding and the expected increase as a result of climate change; Planning authorities should recognize the importance of functional floodplains, where water flows or is held at times of flood, and avoid inappropriate development on undeveloped and unprotected floodplains; Developers should fund the construction and maintenance of flood control that are required because of the development; Planning policies and decisions should recognize that the consideration of flood risk and its management needs to be applied on a watershed basis and not be restricted to floodplains.
Residual risk: there is always a bigger flood; Regardless of chosen safety level, we have to live with a residual risk. In particular related to levees this is a critical issue. The consequences when levees are overtopped are often dramatic. Will we accept them? Climate change: consequences for dimensioning; Legal status: work with other agencies towards a stronger legal status; Definition of classes: simplify and clarify as much as possible to reduce discussions on appropriate class for certain building types; Safety levels: the flood inundation mapping has revealed that the difference in flood level e.g. between a 1% flood and a 0.5% flood is in the order of decimeters. Given the uncertainty in modelling, should the difference between classes in terms of probability be made bigger?
their impact; flood emergency; and prevention of pollution. 2000/60 does not specify specific construction or mapping standards in floodplains, rather it relies on each country’s existing regulations and authorities as the framework to establish guidance. Conclusion Common theme from comparative analysis is that floodplain management is one aspect of watershed management. To effectively address flooding issues necessitates regulations and policy on a watershed level. The EU as well as other countries have recognized this aspect and require action on a watershed basis. ASFPM’s “No Adverse Impact” initiative is leading the United States’ floodplain management debate in this direction. References 1.
http://www.gruppo183.org. Co-operation on Spatial Development 2003-2006.
Floodplain Management in Norway – Integration of Flood Risk Information Into Land Use Planning, Author: Hallvard Berg, Co-author: Tharan Fergus, Norwegian Water Resources and Energy Directorate, European Regional Development Fund Interreg IIIB, 2004.
Seine-Normandie Water Agency Communications and International Services, 1997, NEWSLETTER.
Flood Prevention, Protection, and Mitigation, May 2003.
http://www.ec.gc.ca/water/en/manage/flood/e_origin.htm (Environment Canada).
No building, permitting or financing flood prone development in the designated area.
Suitable for residential, commercial & industrial development, provided that the appropriate minimum standard of flood control can be maintained for the lifetime of the development. Suitable evacuation procedures are required. Generally not suitable for residential, commercial & industrial development. Development should be wholly exceptional & limited to essential transport & utilities infrastructure.
Flood return intervals from 10 to 500 year with a zone without inundation, but with risk of flooding in basements is also calculated.
BINATIONAL PERSPECTIVES ON FLOOD RISK Lisa Bourget and Ted Bailey International Joint Commission Canada and the United States differ in their approaches to flood preparedness, mainly due to constitutional differences in responsibilities for resource management. The United States has a framework at the national level for dealing with flood-related issues through the National Flood Insurance Program, mitigation initiatives under the Robert T. Stafford Disaster Relief and Emergency Assistance Act, and a national mitigation strategy. The 100-year or one-percent chance flood is the national standard for flood insurance and floodplain management purposes, with the 500-year or 0.2-percent chance flood used for any critical action using federal funds. Despite having been recognized through the 1980’s and 1990’s as a leader in flood management with its federal Flood Damage Reduction Program, the Government of Canada has withdrawn from this activity, leaving the responsibility to provincial and local levels of governments. The federal government does maintain Disaster Recovery Financial Assistance Arrangements under the Office of Critical Infrastructure Protection and Emergency Preparedness to enhance the response and recovery capacity of Canadian communities. This program has generally been reactive in nature. The Government of Canada is moving forward with the development of a national disaster mitigation strategy by which all levels of government and interested stakeholders can co-operate effectively to evaluate, prioritize and implement risk and impact reduction measures (Public Safety and Emergency Preparedness Canada, 2004). This may provide a much-needed framework within which flood risk and mitigation activities will be focused. The current Canadian approach is less integrated than that of the United States and tends to be event-driven, with no common programs or frameworks tying activities together. Different provinces have different standards for examining flood risk. British Columbia uses the 1:200 flood generally, but in some circumstances, such as on the Fraser River, uses the flood of record. Saskatchewan uses the 1:500 year flood (International Red River Basin Task Force, 2000). Manitoba’s minimum standard for flood proofing in the Red River Valley is the level of the 1997 flood plus two feet; required building levels in areas of Manitoba outside the Red River Valley are based on the flood of record in those areas (Manitoba Water Stewardship,,n.d.). The International Joint Commission is a binational treaty organization whose mission is to help the U.S. and Canadian governments prevent and resolve transboundary disputes, primarily those associated with water quantity and water quality. In 1997, President Clinton and Prime Minister Chrétien agreed to ask the Commission to study the Red River flood that affected North Dakota, Minnesota, and Manitoba and to recommend means to reduce, mitigate and prevent harm from future flooding in the basin.
at A would have 6m of water over the floor in contrast to B where the depth would be less than 1.0m. For extreme floods, dwelling for town A on the 1 in 100 yr flood line would be inundated over roof level in contrast to those for B which would have less than a metre over floor level. Without providing detailed loss estimates for the two cases it is clear that for A, relative to B, damages will be high and for extreme floods there would be a major risk to life. If consideration is also given to the inclusion of over-floodplain flow velocities there is a very real chance that in an extreme flood the dwelling at location A will experience structural failure with dramatically enhanced damages and a greater risk of death. All too often the unqualified acceptance of a 1% flood standard is set without a hydrological study that provides information on the probable maximum flood, the worst case scenario, or analysis of over-floodplain velocities. A problem enhanced by the practice of colouring on flood maps the land that is below the 1% standard in blue and leaving the land between the 1% standard and the probable maximum flood unshaded. The outcome is that the 1% is frequently interpreted as the line dividing flood free and flood prone. Thus, the consequences of the inevitable extreme flood are for practical purposes ignored. There is also the less obvious link that arises because the 1% standard is often also used as the optimum protection level for structural mitigation works. Risk Management-based Flood Standards Since the mid-1990s emergency management in Australia has shifted its focus to risk management. This commenced with the publication of the Joint Australian/New Zealand Standard on Risk Management (1995), a generic approach for use across the public and private sectors encompassing such diverse topics as financial markets and natural hazards. Emergency Risk Management – Applications Guide (2000), extended the concepts to emergency management. This approach has been incorporated into floodplain management and has led to a much greater emphasis on the identification, analysis, assessment and treatment of flood risk. Specifically this includes serious consideration of the probable maximum flood. In the NSW Manual (NSW Govt., 2001) the key step in council floodplain management is now the preparation of a Floodplain Risk Management Study. This includes the selection of the flood standard to be used by the community and requires that information on flooding extends to the probable maximum flood and that the potential for building failure in response to depth and velocity is considered. This does not in any way simplify the process but it places emphasis on balancing social, economic, environmental and cultural costs of restricting land use and of mitigation measures (especially structural) against the benefits of the reduction in damages, frequency and danger to the community at risk.
Where to next? Worldwide floodplain management policy is firmly based on the use of the 1% standard flood. Although the 1% standard is better than no standard, it is difficult to defend and falls far short of the optimum. The alternative of providing rigorous guidelines for a community to select a locally appropriate standard is unlikely to provide a workable solution. The pre-1986 experience in New South Wales confirms the view that communities are unwilling to set locally appropriate standards even when opportunity and resources are available. However, it is imperative that risks