1、TECHNICAL GUIDEDevelopment, interpretation, and use of rainfall intensity-duration-frequency (IDF) information: Guideline for Canadian water resources practitionersPLUS 4013-12Published in March 2012 by Canadian Standards AssociationA not-for-profit private sector organization5060 Spectrum Way, Suit
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16、umer fibre, is EcoLogo and Processed Chlorine Free certified, and was manufactured using biogas energy.iTECHNICAL GUIDEDevelopment, interpretation, and use of rainfall intensity-duration-frequency (IDF)information:Guidelinefor Canadian water resources practitionersAcknowledgementsThe second edition
17、of this Guideline would not have been possible without the generous financial support of Environment Canada.A Working Group of volunteer experts was integral to the writing and review of this second edition of the Guideline, with a number of members taking on critical Lead Author and Supporting Auth
18、or roles (see Appendix 1). The Working Group was co-chaired by Heather Auld, M.Sc., Risk Sciences International, formerly of Environment Canada, and John Manson, P.Eng., Engineers Canada (Township of Langford, B.C.).The critical feedback and suggestions received during a public review of the first e
19、dition of the IDF Guideline are also acknowledged for their contribution to the technical rigour and improved content of the second edition. Specifically, during the public review over 180 detailed comments and suggestions for improvement were received from stakeholders in industry, research, govern
20、ment, and the practitioner community. These were considered by the IDF Working Group and incorporated into the new edition as was found appropriate and achievable considering both resources and time.Sharon Fernandez of Environment Canada played a key role in coordinating her departments contribution
21、s throughout the development of this Guideline, as did James Waller.PrefaceThis is the second edition of Development, interpretation, and use of rainfall intensity-duration-frequency (IDF) information: A Guideline for Canadian water resources practitioners. It was developed by the CSA IDF Working Gr
22、oup based in part on the first edition of the IDF Guidelines and the detailed comments received through a public review. To submit comments and feedback, please send a message to Inquiriescsa.ca and include “Feedback” in the subject line.As a result of the comments received during the public review,
23、 the second edition of the IDF Guideline contains many changes and improvements from the first edition. These can be broadly organized around efforts to increase the guidelines practicality and applicability to its intended end users and improvements in the technical content of the Guideline. Furthe
24、rmore, two new chapters have been added to the IDF Guideline. Chapter 7 provides an overview of principles for practitioners to use when considering climate change-driven adaptations for water resources infrastructure. Chapter 8 details a number of areas for possible future advancement of the IDF Gu
25、ideline. Canadian Standards AssociationiiEXECUTIVE SUMMARYIntroduction to this GuidelineWater resources management infrastructures comprise one of the largest pools of capital stock owned and operated by municipal, provincial, and federal governments in Canada. In turn, every day Canadians rely on t
26、his infrastructure to help sustain their health and safety, protect their livelihoods, safeguard property, as well as to protect natural systems such as creeks, rivers, and lakes from environmental damage resulting from unintended discharge. In designing and managing these assets and systems, practi
27、cing professionals therefore need to be concerned with the probability of occurrence of extreme amounts of rainfall, often for specific storm durations, since these can result in extensive damage or disruption in services.Traditionally Canadians have relied on Environment Canadas precipitation monit
28、oring networks, sites, and derived climate (rainfall Intensity-Duration-Frequency (IDF) information as the basis for the design, management, and operation of this critical infrastructure. Increasingly, however, the confluence of infrastructure deficitsresulting from aging assets plus the extension a
29、nd intensification of Canadas urban landscapesand better scientific understandings of extreme rainfall patterns have raised concerns about the adequacy of IDF information for certain localities. Evidence that climate change will and may already be resulting in greater rainfall intensities across muc
30、h of Canada has further amplified these concerns regarding the adequacy of “IDF coverage”.In reaction to the above dynamics, parties outside of Environment Canada have begun offering services for the provision of IDF information or, in the case of specific municipalities, have started to generate th
31、eir own IDF information. In some instances, this has relied upon Environment Canada data with the generation of IDF information generally aligned with Environment Canada methodologies. In other cases, data may be used from other sources and methodologies may vary.The goal of this Guideline is theref
32、ore twofold. First, it seeks to provide the guidance necessary to ensure that the derivation and use of IDF information across all Canadian localities is as consistent and scientifically defensible as possible. Second, it provides some of the first formal evidence and advice for the incorporation of
33、 forward-looking information into IDF values and related design activities, such that the effects of climate change can be better considered.To achieve this goal, the Guideline seeks to:(a)Provide to practitioners a basic understanding of meteorological drivers of extreme rainfall that need to be un
34、derstood so that practitioners can determine and meet their local needs;iiiTECHNICAL GUIDEDevelopment, interpretation, and use of rainfall intensity-duration-frequency (IDF)information:Guidelinefor Canadian water resources practitioners(b) Outline how IDF information has traditionally been developed
35、 in Canada, including explanations of the assumptions embedded within current IDF information that are of potential significance for water resources practitioners;(c) Provide guidance to determine if additional precipitation information, including IDF values, is required to optimize the local design
36、 of infrastructure;(d) If new IDF information is required, provide guidance for design and implementation of an enhanced precipitation network, including gauging needs and data requirements;(e) Discuss what the implications of climate change might be for the development, interpretation, and use of r
37、ainfall IDF information and provide guidance on how these implications could be considered;(f) Provide examples of how IDF is currently used in water resources infrastructure planning and design, outline best management practices for management of risks and sustainability and provide guidance on a r
38、ange of adaptation options that address potential changes in rainfall IDF characteristics that could occur as a result of climate change; and(g) Highlight opportunities for expansion in future versions of the Guideline, including treatment of seasonal rainfall events, implications for measuring and
39、monitoring and incorporation of rainfall data that meets variable standards for data quality, as well as additional resources on best practices for factoring in expected climate change implications for IDF information.Intended users of this GuidelineIntended users of the document include: Water reso
40、urce and infrastructure practitioners or other stakeholders who want to better understand the derivation and application of IDF information when generating new or enhanced IDF information (i.e., guidance on establishing monitoring networks and collecting available data, through to the compilation an
41、d derivation of IDF values); Water resource and infrastructure practitioners who need to better understand the derivation and application of IDF information in order to sustainably manage their infrastructure; Water infrastructure practitioners who need to better understand the current and future cl
42、imate drivers of extreme rainfall IDF values and adaptation options to deal with the implications of a changing climate; and Canadian Standards AssociationivEducational institutions, including engineering departments and other disciplines requiring an understanding of the IDF derivation, interpretat
43、ion, and application process.Extreme rainfall Meteorological aspects (Chapter 2)This Chapter of the Guideline describes the meteorology that drives extreme rainfall in different regions of Canada. Since most IDF information is point-specific, in order to judge the applicability of existing IDF infor
44、mation for the design and management of infrastructure at a location other than the precise site for which the IDF values have been calculated (e.g., the Environment Canada station), it is important to have a general understanding of the atmospheric processes driving the occurrence of extreme rainfa
45、ll events at that location. An understanding of the dominant atmospheric processes forcing rainfall extremes is also important for designing rainfall data networks, for interpreting regional climate trend analyses and climate change guidance, and for designing regional IDF and other extreme value an
46、alyses. For example, in regions where smaller scale convective processes dominate, point-specific IDF values may underestimate the true risks of these events across a larger area, and a denser network of rain gauges and IDF sites may be required to better capture the spatial and temporal variability
47、 of the rain events.This Chapter categorizes and describes the four main atmospheric processes that force rainfall extremes, and their influence in different regions of Canada as follows:(1) large scale and longer lasting synoptic storms;(2) smaller scale and shorter duration convective events;(3) t
48、ropical storms or remnants that operate at spatial and temporal scales approaching synoptic storms; and(4) regional orographic processes that are regionally or locally tied to topography and enhance extreme rainfall amounts.The influence of these different atmospheric processes on extreme rainfall v
49、aries across Canada. For example, while the Pacific coast of Canada typically experiences its longer duration extreme rainfall events from synoptic storm systems that originate over the Pacific Ocean or from southerly latitudes, on the Canadian Prairies extreme rainfall events of all IDF durations usually involve convective rainfall processes or synoptic systems with embedded convection.Generally speaking, synoptic events dominate rainfall extremes for durations of about 12 hours and longer, while convective processes tend to influence extreme rainfall events of two
