ARR Update December 2017


On behalf of the Australian Government, Geoscience Australia (GA) has asked the NCWE (a specialist committee of Engineers Australia) to continue overseeing the technical direction of ARR. ARR's success comes from practitioners and researchers driving its development; and the NCWE is the appropriate organisation to  oversee this work. The NCWE has formed a sub-committee to lead the ongoing management and development of ARR for the benefit of the Australian community  and the profession. Current membership of the sub-committee includes Mark Babister, Robin Connolly, Rory Nathan and Bill Weeks.


The ARR team  have been working hard on finalising ARR since it was released in 2016. The team has received a lot of feedback from industry and practitioners, ranging  from substantial feedback to minor typographical errors. Much of this feedback has now been addressed. Where a decision has been made not to address the  feedback, advice has been provided as to why this was the case. A new version of ARR will be released in the first quarter of 2018 with the identified errors  corrected.


A draft of Book 9 Chapter 6 has recently been completed and invitations are being sought  for those interested in being part of the initial review by industry before a broader release. Please email by the 8 January 2018 if you are interested in being involved. It is envisaged that the updated guidelines will be released in their entirety in the first quarter of 2018 for any final comment. Industry will be notified of these dates via the ARR subscriber list.


ARR 2016 is deliberately different to ARR1987, which it replaces. The technical editors and  authors made a decision early in the revision to make ARR 2016 a guideline for modern best practice hydrology analysis. Australian data has been used as well as the latest techniques. It has less focus on providing detailed 'recipes' than was the case in ARR1987, but has been developed to allow application of modern methods supported by accepted engineering research. While this may mean  that there is some additional effort needed to apply these new techniques, this  effort is justified by the improvement in the design flood estimate. Other key  changes in ARR 2016 are summarised at


Following feedback, ARR 2016 will be delivered in a number of formats including PDF. A PDF of the whole document will be produced as well as of individual books. Improvements are also being made to the website referencing. An ePub version of ARR 2016 will continue to also be produced for those who prefer this format.


The ARR Data  Hub will be offline for maintenance on Thursday 21 December. While every effort will be made to minimise outages, it is possible that access may be interrupted  for several days.


Dates and venues for training are currently being finalised and will be announced as soon  as possible via the ARR subscriber list. The training program will feature the editors and key authors of ARR chapters.


In response to numerous requests for the grids of the design rainfalls, the Bureau of Meteorology is providing a service whereby the gridded  data for a specific catchment area will be provided upon request. Requests should be sent to


The digital delivery of ARR 2016 allows minor updates to be made immediately without a complete edition update being required. When major  updates occur, the year will change in the title. Users will be notified of changes by the ARR subscriber list.

ARR Update November 2016

ARR 2016 Guidelines officially finalised

The ARR 2016 Guidelines have now been officially finalised, providing engineers and consultants with the guidance and datasets necessary to produce more accurate and consistent flood studies and mapping across Australia, now and into the future.

Professional engineers and planners, particularly those with local government, are encouraged to make the most of this valuable resource. Consistent use of ARR will ensure that development does not occur in high risk areas and that infrastructure is appropriately designed.

ARR is also now publicly available online and free of charge. Visit to learn more about ARR 2016.

New IFD estimates released by the Bureau of Meteorology

The updated guidelines also incorporate new Intensity-Frequency-Duration (IFD) design rainfall estimates developed by the Bureau of Meteorology, using 30 years of additional observations from over 10 000 rainfall gauging stations and improved statistical analysis techniques. These estimates are used by engineers to understand frequency and likely intensity of rainfall to design better dams, stormwater drainage, to improve floodplain management and assist land managers with soil conservation strategies.

The new IFD estimates are available from

Keeping informed of ARR updates

The digital delivery of ARR 2016 allows minor updates to be made immediately without the complete edition update needing to be made. When major updates occur, the year will change in the title.

Sign-up to the subscriber newsletter to receive details of any future updates to the ARR Guidelines, or alternatively you can follow Geoscience Australia on Twitter.

ARR Update October 2016

Feedback on ARR - closing soon

We would like to remind you that you have until Friday 4th November to provide feedback on the draft 2016 ARR Guideline. You can either lodge it via the contact form on the ARR website or via email to

Your feedback is important to us, as this is the first major update of the guidelines in nearly 30 years.

Once all feedback is received, the editorial team will finalise the document.

ARR software tools

The software tools that were being trialled to assist users with interpreting ARR datasets have been removed from the ARR website. They are now being evaluated by industry as to whether they will be further developed for future use. We will keep you updated on the development of these tools.

Keeping informed of ARR updates

Keeping the ARR up-to-date is an important component for providing reliable and robust estimates of flood risk. We will keep you informed of any updates to ARR through this subscriber newsletter, or alternatively you can follow Geoscience Australia on Twitter.

ARR Update October 2016

Completion of the ARR project

The 2016 ARR is a major achievement as it is the first major update of the guidelines in nearly 30 years.

The modernisation of the ARR Guidelines  has largely been completed. Finalisation of the Intensity Frequency Duration (IFD) data is currently being undertaken by the Bureau of Meteorology, and we will inform you when this is complete.

The modernised guidelines provide engineers and consultants with the guidance and datasets necessary to produce more accurate and consistent flood studies and mapping now and into the future.

A new chapter for ARR

Now that the project is nearly complete, ownership of the ARR has been transferred from Engineers Australia to Geoscience Australia on behalf of the Australian Government. This arrangement means the Guidelines will be publically accessible free of charge.

The transfer will include transitioning the ARR website to a new website domain -

Keeping informed of ARR updates

Keeping the ARR up-to-date is an important component for providing reliable and robust estimates of flood risk. It also provides necessary information for locating new developments in safer areas, and appropriately designing new infrastructure.

The digital delivery of ARR 2016 allows minor updates to be made immediately without the edition being updated. When major updates occur, the year will change in the title. The website will be regularly updated to ensure the ARR Guidelines remain current.

We will keep you informed of any updates to ARR through this subscriber newsletter, or alternatively you can follow Geoscience Australia on Twitter.


The industry launch of ARR guidelines is occurring as part of the Engineers Australia Hydrology and Water Resources Symposium, Hobart 2015. The industry launch will include Books 1, 2, 3, 6, 8 and 9. ARR has been prepared on a book and chapter basis with 9 books and 40 chapters. The editorial and review process, test program and the practitioner working group have highlighted some internal consistency issues between books and chapters that have to be addressed. These problems have arisen from the late delivery of some content, the complexity of combining content from over 100 contributors and learning experiences from the test program. On the basis of feedback received to date the key issues that need to be addressed are:reconcile inconsistencies found in the integration of new design inputs,

  • potential changes to rare design rainfall
  • more accessible guidance for practitioners,
  • correct balance between new techniques and established approaches,
  • consistency in terminology and style,
  • more detailed worked examples, and
  • fine tune guidance based on the test program.

These changes are necessary to ensure that the document receives wide acceptance by the target audience. The review has resulted in the need to rework books 4, 5 and 7 which cover catchment modelling processes, hydrograph estimation and the application of these modelling approaches. There are also some minor flow on effects for books 8 and 9 but these are relatively minor and will not affect their release.

Although not complete there has been significant progress and the release at HWRS of what has been completed will be a significant milestone in what has been a very large and complex project.

ARR WSUD Workshop 19th October

The ARR team, in conjunction with the 9th International WSUD Conference, are running an workshop to discuss the latest developments in the ARR revision, specifically in the WSUD and urban drainage space.  Topics covered will include an overview of the new short duration IFDs and synthetic rainfall for continuous simulation as well as the design of retarding basins.  Dr Peter Coombes will also be presenting on current directions in urban drainage.

When ARR is released there will be significant changes to the recommendations and guidelines across the hydrologic sector, with major flow on consequences to engineering and ecologic practice. This workshop is intended to introduce these changes to practitioners working in the fields of WSUD, short duration design and analysis as well as continuous simulation for process modelling. It is also a significant opportunity for industry practitioners to provide feedback to ARR authors and the editorial team into the direction and final outputs of ARR, which is scheduled for launch later this year.

Draft Timetable

0930-0945WelcomeMark Babister
0945-1000Major Changes to Urban CatchmentsJames Ball
1000-1030Outline of the New Runoff In Urban Catchments, Book 9 or ARRJames Ball
1030-1100Morning Tea 
1100-1130Temporal Patterns and Their Influence on DesignMark Babister
1130-1200Urban LossesRhys Thomson (TBC)
1200-1245Urban Drainage and the Urban Water CyclePeter Coombes
1330-1400Retarding and DetentionBrett Phillips (TBC)
1400-1430Generated Continuous Rainfall SequencesAshish Sharma
1430-1500Frequent RainfallJanice Green
1500-1530Afternoon Tea
1530-1545Coastal InteractionTBC
1545-1630Discussion Session/TBCTBC

ARR Update March 2015

Book 3 - Peak Discharge Estimation released for industry comment

The ARR team is pleased to announce the first complete draft book of the 4th edition of Australian Rainfall and Runoff is released for industry comment. Book 3 covers both regional and at site flood frequency estimation techniques. The at site flood frequency chapter is a significant change from the version previously available (Kuczera and Franks, 2006) and supersedes this version. Please note that this is a draft and as such some of the figures, examples and formatting have not been finalised. The report will be available for industry comment until the end of April. Software for the regional flood frequency estimation method is in the final stages of testing and will be released soon. FLIKE will be also be commercially available for a small price from TUFLOW in the near future.

Project 5- regional flood methods - stage 3 report release

In conjunction with the release of Book 3 Chapter 3 Regional Flood Frequency Estimation the Project 5 regional flood methods stage 3 report and data report by the University of Western Sydney team (lead by Dr Ataur Rahman) are being released. This report provides more detail on the method and supplements the chapter. Stage 3 is the final stage of the project which began in 2008. Thank you to all the project team, state teams and government organisations that provided data for this nationally significant project. This project is a significant advance on the techniques in ARR 1987.


To accompany the release of Book 3 chapter 3 Regional Flood Frequency Estimation we are also releasing a short background video on the development and implementation of the method. The video is available on the ARR youtube station.

Hydrology and Water Resources Symposium

The 36th Hydrology and Water Resources Symposium will be held 7-10 December 2015 in Hobart, Tasmania. This event, hosted by Engineers Australia and its National Committee on Water Engineering, is Australia¿s leading symposium devoted to hydrology and water resources.

The industry launch of the revised edition of Australian Rainfall and Runoff will be held at the symposium. A session will be dedicated to ARR papers.

ARR Update February 2015

Initial testing is currently underway to ensure all data required for the tests are available. This has included making sure the catchments are suitable and the methodology is complete. While this has taken longer than expected we feel it is important that the testing be as straight forward as possible and not time consuming for the testers. We anticipate this will be complete soon and will keep you updated on progress.

With the new edition entering its final months we thought it time to clarify some terminology and referencing. You may have noticed with our logo and communication we are using ARR as the preferred acronym for Australian Rainfall and Runoff.
ARR has a long history. With 3 full editions published and a 4th currently nearing completion.
Edition 1 - 1958 - Australian Rainfall and Runoff - First Report of the Stormwater Standards
Edition 2 - 1977 - Australian Rainfall and Runoff - Flood Analysis and Design
Edition 3 - 1987 - Australian Rainfall and Runoff - A Guide to Flood Estimation
The upcoming edition will be referred to as ARR 2015 or the 4th Edition or version of ARR.
Note: the 1987 edition was republished in book form in 1997. With only the chapter on the estimation of extreme to large floods updated in 1998. A lot of people reference the 2001 edition which is just a reprint of the 1998 edition.
We recommend people refer to the full editions or directly refer to an updated book or chapter. For example a reference to the rational method would be to ARR 1987 (see below for a complete reference). A reference for large floods would be to Book VI by Nathan, RJ and Weinmann, E, (1998) (see below for complete reference).

How to reference editions/chapters/books/project reports

The following guidelines are recommended when referencing Australian Rainfall and Runoff (ARR).
Each time a revision is published, the reference to Australian Rainfall and Runoff changes to the date of that year.
For example:
Pilgrim, DH, (ed)., Australian Rainfall & Runoff - A Guide to Flood Estimation, Institution of Engineers, Australia, Barton, ACT, 1987.
Reference to specific books or chapters, for example:
Pilgrim, DH and Rowbottom, IA, Estimation of Large to Extreme Floods, Chapter 13 in Australian Rainfall and Runoff, A Guide to Flood Estimation, Volume 1, DH Pilgrim (ed), The Institution of Engineers, Australia, Barton, ACT, 1987
Nathan, RJ and Weinmann, E, (1998) Estimation of Large to Extreme Floods, Book VI in Australian Rainfall and Runoff
- A Guide to Flood Estimation, The Institution of Engineers, Australia, Barton, ACT, 1998.
Reference to the draft chapters of the forthcoming revision of ARR, for example:
Kuczera G and Frank S, Australian Rainfall and Runoff, Book IV, Estimation of Peak Discharge-Draft, Engineers Australia, Jan 2006, downloaded 12 July 2012

To reference ARR Revision project reports, for example:
Hill P, Graszkiewicz Z, Taylor M, and Nathan R, 23 October 2014, Australian Rainfall and Runoff Revision Project 6: Loss models for catchment simulation: Phase 4 Analysis of Rural Catchments, ARR Report Number P6/S3/016B, ISBN 978-085825-9775

Did you know that ARR has released a discussion paper on the preferred terminology for ARI and AEP?
The term x year ARI has caused confusion both within the industry and with the community and other stakeholders. It has been interpreted by many to imply that the periods between exceedances of a given event magnitude.
The preferred new terminology is AEP and EY. Annual Exceedance Probability (AEP) where AEP expresses the probability of an event occurring or being exceeded in any year. Additionally, AEP are to be expressed as an exceedance probability using percentage probability; for example, the 1% AEP design flood discharge. Extreme flood probabilities associated with dam spillways are one example of a situation where percentage probability is not appropriate. In these cases, it is recommended that the probability be expressed as 1 in x AEP. Note that it is incorrect to express ARI as 1 in x year ARI or AEP as 1 in x year AEP.
For more frequent events an annualised exceedance probability is misleading and confusing. Furthermore, a recurrence interval approach also is misleading where strong seasonality is experienced. Consequently, events more frequent than 50% AEP should be expressed as x Exceedances per Year (EY). For example, 2 EY is equivalent to a design event with a 6 month recurrence interval when there is no seasonality in flood occurrence.

The blockage guidelines have now been finalised based on feedback from industry and the results of the initial testing.

ARR Update November 2014

Climate Change Guidelines

This draft discussion paper draws on the most recent climate science, particularly the release of the IPCC Fifth Assessment Report on the Physical Science Basis in September 2013 (IPCC, 2013) as well as the new climate change projections for Australia (CSIRO and BoM, 2014), and outlines an approach to address the risks from climate change in projects and decisions that involve estimation of design flood characteristics. For consistency with the revised IFD design estimates for Australia, the Interim Guideline is intended to be applied to current-day rainfall intensities with a probability of one exceedance per year or annual exceedance probabilities (AEPs) from 50% to 1%.

The launch of the draft discussion paper was held on the 26th of November at the Convention as part of the Practical Responses to Climate Change Conference.

The draft discussion paper is now available on the Project 1 page. Comments on the Climate Change Guidelines will be accepted until the end of February 2015.


Phase 4 - Analysis of Data for Catchments across Australia is now available on the ARR website. Loss values have been derived in a consistent manner from the analysis of recorded streamflow and rainfall from catchments across Australia and then analysed to determine the distribution of loss values. Finally, prediction equations were developed that relate the loss values to catchment characteristics.