A spreadsheet (Lotus 1-2-3) based technique for analysing storm suspended sediment data with particular reference to logging disturbance in tropical forests

The procedure describes a simple and functional method using a commercial s preadsheet (Lotus 1-2-3) to calculate water and sediment yields from measur ed or given data sets. Suspended sediment concentrations are located on a s torm hydrograph and concentrations for unsampled points on the hydrograph a re estimated using the principle that the change in concentration between t wo sampled points will be proportional to the change in discharge between t he same two points. The relationships are then solved by a cross-correlatio n equation using simple formulae in the form of triangle-square equations t o calculate water and sediment yields between each sample time. The techniq ue is applied to a 51 month data set from a long-term monitoring programme assessing the impacts of commercial logging operations in Sabah, East Malay sia. Yields for the monitoring period derived by the spreadsheet technique are compared with results from the application of more traditional discharg e-sediment rating techniques. In the undisturbed catchment, yields derived from some rating equations compare favourably with the spreadsheet techniqu e. However, in the disturbed catchment, rating techniques proved less appli cable because of the continuously changing nature of the catchment in relat ion to vegetation recovery, exacerbating variation and scatter in the data set. The application of the spreadsheet technique provides detailed informa tion at an individual storm level; however, working with the method on long -term discharge records requires a significant commitment of time as compar ed to the straightforward application of rating equations. (C) 1998 John Wi ley Bi Sons, Ltd.