Landforms

The catchment is dominated by mountains and hill country. 

The mountains are characterised by strong lithologic and structural control of landforms, with dip and scarp topography common and notable areas of karst on Mt Owen and Mt Arthur. 

The hilly terrain can be grouped into three types:

• intensely fluvially dissected hill country on Moutere gravels, with linear, regularly spaced valleys and ridges;

• smaller areas of dip-and-scarp topography on young sedimentary rocks; and
• smoothly rounded hill country on granite.

Slopes

About 67% of the catchment has slopes greater than 15º. 

There are limited areas of gently sloping floodplain, terraces, and fans.

The Motueka-Riwaka Plain

The two most extensive flat areas are the 40 km² Motueka-Riwaka Plain near the coast and the 33 km² upper Motueka.