The Waiapu River is formed with the joining of the Mata River, which flows north-east from the Raukumara Ranges, with the Tapuaeroa River near Ruatoria township. The Waiapu is perhaps the most famous river in our region from a perspective of pre-European history. Its name is found in Tahiti and it offers a protected region where people could settle and find safety in times of war. The river valley is referred to in a tribal saying: “Hoake taua ki Waiapu ki tatara e maru ana.” In English this means “Let us shelter under the thick matted cloak of Waiapu.”
Further inland, the Waitohaia River flows into the Mata River.
The Waiapu River has a catchment of 173,400 ha, much of which is very prone to erosion. Much progress has been made over the past 40 years in afforesting the eroding areas and encouraging areas to return to indigenous scrub, but the Waiapu remains the most sediment laden river in the Gisborne District. The annual suspended sediment load is 36 million tonnes. This translates to 90.47 cubic metres of sediment flowing out to sea per second.
The eroding gravels are rapidly raising the bed of the river in the lower reaches, causing riverbank erosion that is threatening Ruatoria township. A number of bridges over tributaries have been raised in recent years in response to rising riverbeds. The river catchment is mostly covered in native bush (more than 80%) with the remaining area covered in scrub and coastal forest.