Catchment sediment load limits to achieve estuary sedimentation targets

Abstract

Limits are needed to manage the cumulative effects of sediments in estuaries. A method of calculating catchment sediment load limits to achieve estuary sedimentation targets is presented. The method is based on manipulating the sediment budget and takes advantage of the inherent complexity of the estuary and its connections to different sediment source regions in the catchment. In all but the simplest of cases, there is never just one way to achieve estuary sedimentation targets. This is where opportunity lies, for some ways of achieving targets will be better than others. Management can focus on finding sediment load limits that do not fail any sedimentation targets and that are achievable, affordable and efficient. The latter is expressed in terms of sacrificing capacity of the estuary to accommodate sediment in order that no sedimentation targets are failed. The method and underlying principles are demonstrated by application to Pāuatahanui Inlet, New Zealand.