Stream roughness is a critical parameter for open channel flow calculations and has an important influence on hydrographic and engineering practice. In many cases the selection of an appropriate stream roughness coefficient, such as Manning’s n, is required, but often this is not straightforward. In other countries, particularly New Zealand and the United States, roughness coefficients have been collected for broad classes of streams, different types of vegetation and specific flow conditions. Pictorial guides or empirical equations, provide a firm basis for estimating these roughness coefficients. In some cases these guides are applicable to Australian conditions, but there are also many Australian streams that are not well covered by existing handbooks. lt is also recognised that improved techniques to estimate roughness coefficients have the potential to provide benefit to those working in the area of hydraulics, including hydrographers, and to reduce costs to society.
lt is now proposed to develop an Australian Handbook of Stream Roughness Coefficients. This will build on existing guides, and equations, and test their applicability through a series of case studies. Information collected by hydrographers will be a vital part of this effort. Roughness calculations can be made at any site where there are measurements of discharge, water surface slope and cross section dimensions. Any contributions of these data would be valuable and we invite hydrographers to collaborate in this project. Results from this work would also be available for use by hydrographers.