Distance: 9.2 km (4.5 DOC hours) - Unmarked route, clear - Moderate terrain
Altitude: 338m to 743m. Gain: 543m. Loss: 213m . Gradient: 5 deg (Moderate)
Skills: - Prolonged rivers (4/6)

Unmarked route, clear (7/9)
Unmarked route, follows obvious geography (river, spur, trail, etc)

Secondary, mapped (3/5)
Formal route, on maps, an alternative recognised access to hut or along range / catchment

Moderate (difficulty: 3/5)
Occasional moderate climbs

Moderate (difficulty: 3/5)
Low scrub in open or bush / river rocks

None (difficulty: 1/7)
No alpine skills required

Prolonged rivers (difficulty: 4/6)
Frequent river travel - impassible after rain, risk of getting trapped

None (difficulty: 1/7)
No alpine skills required

It'll be cold and potentially flooded...

Gentle amble up the Otaki river with numerous crossings. A few waist deep pools, but really nice travel when river levels are low. Pass several good sized streams coming off the main range with potentially good travel up them to the tops. There are also several old monitoring sites on the terraces above the river that you may see through the bush.
Not a route for bad weather.
At the sharp bend to the east, we climbed (scrambled) up the bank and climbed up to the main spur to the Te Matewai Hut track. There is an old track with markings still visible - I suspect it is slightly further up the river than this shows. The initial climb up is steep.

Note: Described in the reverse direction to your journey

Find the tree with numerous markers on it and head south-west down the spur. There is an old marked 'track' to follow down into the Otaki River. Once in the river, it's a gentle wander down the valley. There are some waist deep pools.
Not a route for bad weather.