Design rainfall for South Africa: RLMA&SI station, grid and parameter data (WRC 1060/1/03)

This dataset contained the design rainfall data developed in WRC project K5/1060 (Smithers and Schulze, 2003, WRC Report No. 1060/1/03) and distributed with the Design Rainfall Estimation in South Africa (DRE-SA) software, version 3 (2012). The project developed the Regional L-Moment Algorithm and Scale Invariance (RLMA&SI) procedures, which were used to estimate design rainfall depths for durations from 5 minutes to 7 days and return periods from 2 to 200 years at any location in South Africa. The procedures superseded the TR102 storm rainfall values (Adamson, 1981) for most engineering applications.

Four resources were provided. The station database contained 1- to 7-day design rainfall depths, with lower and upper 90% bounds, for return periods of 2 to 200 years at 3 946 South African Weather Service daily rainfall stations, together with station coordinates, MAP, altitude, record period and cluster. The national grid contained 421 027 one-minute cells with MAP, altitude, daily, short-duration and regional cluster memberships, the adjusted mean of the 1-day annual maximum series, and the percentage prediction errors used to derive 90% bounds. A lookup workbook contained the 1-day growth curves for 78 clusters, the regional regressions for 2 to 7-day durations, the short-duration regressions for 15 clusters, the 24 h to 1-day ratios and a data dictionary. A fourth workbook contained all ten tables printed in the report.

The grid and lookup tables were read directly from the DBF files distributed with the software, without modification apart from added decimal-degree coordinates. Report tables were harvested from the born-digital report and checked against the rendered pages, and suspected errors in the source were listed for verification. Design depths at any grid cell could be computed by multiplying the cluster growth factor by the adjusted 1-day mean and applying the duration relationships described in the report.