A spreadsheet (Lotus 1-2-3) based technique for analysing storm suspended sediment data with particular reference to logging disturbance in tropical forests
T. Greer et al., A spreadsheet (Lotus 1-2-3) based technique for analysing storm suspended sediment data with particular reference to logging disturbance in tropical forests, EARTH SURF, 23(13), 1998, pp. 1235-1246
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.