Optimising drainage from sugar cane fields using a onedimensional flow routing model: a case study from Ripple Creek, North Queensland

Inundation of sugar cane fields in the Ripple Creek catchment is perceived by some cane farmers to be a major contributor to loss of production. To alleviate this inundation, drainage systems have been designed which are capable of removing surface water very rapidly. However, when the Herbert River is in flood this water may have nowhere to go. This combination of an efficient drainage system, the lack of an outlet for the water, and the growing of cane on land which may be unsuitable, has led to some farms facing extended periods of inundation. For this reason, proposals have been made to the Ripple Creek Drainage Board to modify the drainage system to produce a more equitable distribution of inundation. In this paper, we examined the application of the Mike-11 modelling system to the Ripple Creek catchment. We found that the modelled predictions of depth, discharge and velocity matched observational data collected as part of an intensive CSIRO monitoring program. The model developed was then used to examine the hydrologic impact of opening a new channel to divert flow into the Seymour River. We found that opening this channel had some impact on indundation in parts of the catchment, but that the impact depended on whether or not the Herbert River was in flood at the time.