The Usuthu River forms part of the international boundary between South Africa and Mozambique. In 2002, this River breached its south bank within the Ndumo Game Reserve and established a new channel within the protected area. In response to the breach, Mozambique proposed the excavation of the floodplain and the establishment of berms to force the flow of the river back into its original alignment. Analysis of the origin and associated history of this portion of the international boundary indicates that it is unlikely that the international boundary has moved with the breech. Furthermore, customary international law pertaining to the avulsion or mutation level of rivers supports the notion that the international boundary remained in the original channel of the Usuthu River. Finally, case history of a similar circumstance in Africa affirms that this boundary is unlikely to have shifted with the avulsion of the Usuthu River. The Mozambican proposal brings to the fore an array of public trust considerations which are founded in South Africa’s Constitution, and environmental and biodiversity conservation legislation. These considerations prohibit the excavation of the Ndumo Game Reserve. The concept of the state acting as a trustee for, inter alia, biodiversity, and protected areas, is reinforced by various water and biodiversity-orientated multilateral agreements to which South Africa is a signatory. Within these, the ones adopted by the Southern African Development Community are the most profound in that they, and specifically the Protocol on Wildlife Conservation and Law Enforcement, enjoin state parties from taking decisions that may cause damage to the trust entity beyond the limits of their sovereignty.
