[Edit 17 Oct 2016: Some web links have changed. See Where is ARR?]
A new draft version of Australian Rainfall and Runoff has just been released and is available for download here. The epub file is dated 2016-07-07.
So, what has changed? After skimming through the document, my preliminary assessment is as follows:
- There is now more than one editor. The previous version listed James Ball as the editor while this one lists James along with: Mark Babister, Rory Nathan., Bill Weeks, Erwin Weinmann, Monique Retalick and Isabelle Testoni, with Peter Coombes and Steve Roso associate editors for Book 9.
- Industry consultation on the current draft will take place until October 2016 when the editorial team will meet to consider feedback and decide on when the next update will be published.
- Referencing has been improved and many in-text citations are hyperlinked to their location in a reference list.
- Book 2 Rainfall Estimation, Chapter 1, Introduction, has been re-written.
- There is a new chapter on climate change impacts on rainfall (Book 2, Chapter 2.7).
- Book 2, Chapter 4, has a name change, from Spatial Patterns to Areal Reduction Factors. Alan Seed is no longer listed as an author. Spatial patterns are now addressed in a new chapter (Book 2, Chapter 6).
- Book 2, Chapter 4, Areal Reduction Factors: the equations used to calculate areal reduction factors have changed (but are still difficult to interpret, at least on the epub version).
- Book 2, Chapter 4, Figure 2.4.1: The ARF regions map looks different but it may just be a change in colour scheme.
- Book 2, Chapter 5 – the chapter on temporal patterns has been greatly expanded and design patterns are now available at data.arr.org.au (although the website is currently unavailable). The example in Book 2, Chapter 5.10 shows the use of design temporal patterns in RORB modelling.
- Book 2, Chapter 7 now covers continuous rainfall simulation (mainly just a change in Chapter numbering).
- Book 3, Chapter 3.12. This is a new chapter: RFFE Implementation and Limitations, which includes a discussion on the likely accuracy of the RFFE and additional checking to be undertaken when using the tool.
- Book 4, Catchment Simulation. There was no content in this book in the Dec 2015 version of ARR. Now a draft of the whole book is available (Disclosure – I’m the lead author of Chapter 2).
- Book 5, Flood Hydrograph Estimation, has been extensively revised. There are new chapters on: catchment representation (Book 5, Chapter 2); flood routing principles (Book 5, Chapter 5); and flood hydrograph modelling approaches (Book 5, Chapter 6).
- The losses Chapter (Book 5, Chapter 3) has been revised. There are new methods to select losses for design flood estimation (Chapter 3.5). The loss regions have changed (Figure 5.3.16). There are now only 4 regions and new prediction equations are available for each region. Median IL and CL values for much of Australia are provided in Figures 5.3.18 and 5.3.19.
- Book 6, Flood Hydraulics, was well advanced in the previous draft but there are several updates. The chapters on Rock Chutes and Rock Riprap have been removed and a new chapter on safety design criteria has been added (Book 6, Chapter 7). This was previously in Book 9.
- Book 7, Application of Catchment Modelling Systems, is now available as a complete draft. There was no content in the December 2015 version of ARR. This Book includes information relevant for hydrologic models, RORB, RAFTS, URBS and WBMN.
- Book 8, Estimation of Very Rare to Extreme Floods was well advanced in the Dec 2015 draft ARR and a quick review suggests there have been few changes.
- Book 9, Runoff in Urban Areas was not included in the earlier draft. It was available as a separate PDF but is now integrated into ARR. All of Book 9 is now available except Chapter 6 ‘Modelling Approaches’.
- The safety design criteria information from the earlier version of Book 9 has been moved to Book 6.
One issue that is not specifically addressed is the continued use of the urban rational method. It is not included in the urban book (Book 9) and the subtext is that there are better approaches. However, the urban rational method is widely used in practice and is recommended by some authorities e.g. Melbourne Water (see their hydrologic and hydraulic design guidelines here).
A general issue is that authority guidelines and standards will need to be updated to relate to the new Australian Rainfall and Runoff. For example the Austroads Guide to Road Design, Part 5: Drainage – General and Hydrology Considerations, refers to the 1987 version of Australian Rainfall and Runoff. There is a similar issue with the stormwater drainage code, AS/NZS3500.3.