The impact of the simulated error in the DSM on the slope derivative is shown in the standard deviation for slope. The maximum standard deviation is 3.2◦. The greatest variability in slope values is found on the steepest slopes, whereas the flat areas show very limited variability. Finally, the standard deviation for the flow accumulation shows that the greatest impact of the simulated DSM error occurs in areas where the flow accumulation is high. The standard deviation in flow accumulation shows a significant spatial variability within the existing stream channels. The Monte Carlo simulation has the greatest effect on flow accumulation as it forces the stream channels to ‘jump around’ between iterations by introducing subtle, but significant, variations in height values. The DSM did not cover the full spatial extent of the ridge line, which means that the watershed is larger than the DSM. This has implications for flow accumulation modelling in that the upstream area is larger in reality than what can be derived from the DSM. Given the morphology of the study area, we do not expect this to have a substantial effect on the analysis, however, for future field visits we plan to capture the complete watershed to account for the edge effects.