What is the Need to Revise AR&R?

Many of the practices recommended in the 1987 edition of AR&R are becoming outdated and no longer representing the accepted views of professionals, both in terms of technique and approach to flood management. Coupled with a greater understanding of climate and climatic influences the securing of current and complete rainfall and streamflow data and expansion of focus from extreme flood events to the full spectrum of flood flows and rainfall events, makes the updating of ARR crucial to allowing better management, policy and planning decisions to be made in respect of frequent and rare flood flows.

There is also a growing need to recognise issues reflecting the changing views of the community and to deliver information and solutions relevant to these issue inclusive of:  

More recently as part of the preparation of the revised edition, views of users have been sought through presentations at all Divisions of Engineers Australia. At these presentations the traditional focus of Australian Rainfall and Runoff nas been discussed as well as the need to provide additional information on the hydrology of rainfall and runoff for water quality investigations in both urban and rural areas, the use of catchment simulation techniques, the integration of hydrologic and hydraulic models, and hydrological aspects of integrated water management within urban areas. These views and other feedback formed the basis of the structure proposed for the new edition.  

While these changes in the needs of users have resulted in changes in the proposed layout for the current revision of Australian Rainfall and Runoff, the general layout has remained one of separate books integrated together to provide the relevant information. The more significant changes have occurred within the proposed books through the material incorporated and discussed therein. 

The major knowledge gaps in the current edition of ARR can be consolidated into three major categories which are:  

  1. Insufficient and incomplete rainfall and streamflow data;
  2. Inadequate advise on modelling and simulation techniques using catchment modelling systems; and
  3. Too narrow a focus on only major and extreme floods instead of the complete spectrum of flood flows from annual flood flows to extreme flood flows.

These concerns will be allayed by:  

  1. Utilising the most complete and up-to-date data sets possible from across the country and considering climate change and factors that influence rainfall and streamflow patterns;
  2. Revising current methodologies and verifying and implementing new techniques, calibrated on both a local and regional scale, able to be used by the profession across the country; and
  3. Broadening the focus of ARR to consider the full spectrum of rainfall and streamflow events, complementing the conventional focus on extreme flood events with nationwide applicability.

Furthermore, factors such as climate change and persistent climatic states have been found in numerous scientific studies to have significant effects on Australian hydrological patterns. Through including all available data into the development of revised IFD relationships, recently developed trends and periodicities in data can be accounted for in the analysis stage, delivering more accurate and reliable estimations of design rainfall. The situation is compounded when it is considered that IFD relationships and, to a greater extent, rainfall analysis, form the basis for much of the analysis of flood events, including estimations of flood frequency and magnitude.  

Without reliable estimations of rainfall, flood estimation is severely compromised and, given that AR&R provides the source for virtually all flood mitigation and hazard studies and planning, it is alarming to consider the potential for error in these studies and the potential damage in economic, environmental and social terms that erroneous information and conclusions could cause.

Image of a house built over an urban creek.