Altitude: 99m to 926m. Gain: 874m. Loss: 816m . Gradient: 8 deg (Moderate-hard)
Skills: Prolonged scrambles (4/7)
From the bend 2km below Lake MacKinnon deer trails initially follow both banks of the Large Burn upriver on river flats. However as the river starts to climb towards the lake outlet ground becomes steep and bouldery and it is necessary to sidle the base of faces on the true right of the river generally 10-20m above the river. These faces can be followed to the back of the small bay avoiding swampy ground at the lake outlet, before dropping to the lakeside flats and bashing through to the lakeshore where there should now be good gravel beaches.
Follow good gravel beaches south along the lakeshore. There are numerous grassy flats behind the beaches, but all are only 1-2m above the lake and reportedly flood - and have no high land nearby to escape to. For those wishing to camp, there are a couple of good flat spots back in bush on the peninsula half way round the lake: 5m or so above the lake level and on a good spur that could be ascended in case of water levels rising, and only 10-15m behind the beach.
The final 800m of lake shore is steep and must be sidled across steep faces littered with windfall. On slip provides additional challenges with the best crossing at the time I visited being about 30m above the lake.
Above the lake the flats are initially marshy and thick with pepperleaf scrub, but soon firm up as you head upriver. Reasonable deer trails head up the true right bank providing ok (for Fiordland) travel until 1km below the head forks. As the valley starts to climb, deer trails peter out and you are left scrambling boulder-strewn flats and pushing through thick undergrowth and windfall (again).
The head forks are obvious with the creek splitting initially in 3 (the western-most branch forks again 20m upstream making the 4 forks shown on the map). The route to the saddle is up the spur just south of the fork which heads due west. Deer trails are initially patchy but firm up as you climb due west, sticking on the small spur near to the western creek and swinging south with it as the creek swings that way. Windfall on the narrow upper spur proves challenging as there is no real way round it and some steep, exposed scrambles result to reach the bushedge.
Bluffs are visible just above the bushedge, and a reasonable deer trail follows the base of these bluffs climbing south to hit the saddle at its north-western end, dropping occasionally to sidle int he thick scrub. Once on the saddle an easy stroll takes you down swampy grassy flats to the basin draining into the Irene. There are viable dry-ish campspots on the saddle near boggy tarns.
The obvious spur shown on the map dropping from pt962 to knob pt559 is steep and bluffed in places and has no deer trails. The key seems to be to descend the face just north of the obvious spur and aim to hit the swampy saddle behind pt559. Once on pt559 clear deer trails commence and descent the at-time very steep spur to the Irene below, exiting into the sidecreek just south of the spur maybe 50m from the main river. The entire descent is very slow in hard terrain and vegetation - allow plenty of time.
Cut south across the rocky fan debris to reach the bottom end of broad open flats in the Irene. Good, flat, dry, well-used campspots exist in grassy clearings amongst young beech on the western bank - through these presumably flood in extreme conditions.
Base of Doon valley pass to Lake MacKinnon beaches: 3km, 2-3 hrs
Lake MacKinnon beaches to Large Burn - Irene saddle: 8km, 6-10 hrs
Large Burn - Irene Saddle to Irene valley flats: 2km, 2.5-3.5 hrs