Design flood estimation for small rural catchments in South East Queensland

Abstract

The estimation of peak flood flows for small (max. 25km2) to medium (max. 250-1000km2) sized catchments is probably the most common design work undertaken by water engineers. Almost half the national average annual expenditure is spent on works of these size, including culverts, small-medium bridges, causeways, spillways on farms, other small dams and soil conservation works. The current Rational Method described for the Queensland region, in Australian Rainfall and Runoff, is not suitable as it has not been derived from observed flow data. Other methods that have been produced are respectfully found to be inadequate for the South East Queensland region based upon the values of runoff coefficients produced. A consistent and easy to use procedure has been developed has been developed. Using the following formula and table, combined with general procedures for use with the Rational Method, consistent and reliable peak flood flows can be derived for use in design.