It was some of the most logistically intense, high risk, strangest, and surprisingly most enjoyable fieldwork I have done to date. Back in the late 1970s a triangulation network of 6 stations was set up across the Alpine Fault at Lake McKerrow in the Lower Hollyford Valley. Each station consisted a stainless steel survey pin and galvanized angle iron set into a large slug of concrete. By measuring the position of each point relative to each other using angles and distances, and then later resurveying the network, the surveyors would be able to determine whether the fault was locked and building for the next earthquake, or exhibited a component of fault creep. The last of these surveys ended in 1984, possibly not enough time to measure a component of creep above the uncertainty. The discovery of saponite-rich gouge with identical physical properties as the creeping portion of the San Andreas Fault at the nearby Hokuri Creek prompted a heightened interest in trying to conclusively prove whether is or is not, actively creeping. The chance to collect over 30 years of fault data is a rare opportunity which could yield some important results. And so started the great Fiordland high-risk scavenger hunt....
The first (and easiest) monument we found
All I had to do was find these six 30cm x 30cm monuments, occupy them
with a high precision GPS (mm accuracy) for 18hrs each and then later compare the data
to the original surveys. Problem is I had hand drawn sketches pointing
me to the station locations with descriptions like "~15 m from the shore
and 10 m from a prominent tree"...Fiordland
is not known for being one of the more static places in New Zealand,
let alone the world, so it would certainly take some persistence and
luck. Nevertheless I was confident I could narrow the area down to less
than 50m in most cases and hoped a metal detector could aid us from there. In order for success we needed to find five or six of the monuments. The monuments were also on both sides of a 2km wide lake, which would have discouraged most. I was confident that in most wind swell conditions Jeff and I could comfortably use our Alpackas to traverse back and forth as needed (but I was also aware of the abrupt and dramatic changes this lake could undergo). We also would have to design our campaign to make the most of the limited time and 2 GPS units. This meant initially occupying the easiest to find stations, then searching for the harder to find ones while data was being recorded.
We were able to get a helicopter backflight into Hokuri Hut where we had a frantic hovering landing due to the lack of beach from the high lake level. We quickly unloaded at the hut and set off to make the most of the remainder of the day. We inflated our packrafts on the beach and carefully loaded the heavy GPS equipment (5lb GPS unit, cables, antennae, spike mount tripod, level, etc.) into our slightly precarious boats. We quickly and easily found monument Z and carefully leveled the GPS above it. We then paddled the long 3km crossing over to the other side of the lake. Despite the wind chop we made it ok and promptly found and occupied monument C. Those first two monuments were of course the easy ones. We still had several hours of daylight so we set off along the coast to look for B. We landed at the logical location indicated by our sketch and set off narrowing the location down. Before long we identified the likely beach ridge and I tried to find it visually while Jeff used the metal detector. He got a strong hit in one location and I found an old plastic mug to dig with. Amazingly, buried 0.5m beneath modern beach gravel, we found monument B! Carrying on we had a quick look for A before crossing the lake back to the hut just before dark. It was clear A was going to be the tricky one- the "lone beech tree" and "rock pile" indicated as key landmarks were nowhere to be seen 30 years later! We did meet a couple friendly builders working on a private hut who would later be of great help.
Metal detector says dig here
Monument B, buried beneath 0.5 m of modern beach gravels!
Day 2. Greyer with intermittent rain. Found monument Y buried immediately beneath the path to Hokuri Hut! Found battery on Z to have been dead! I had a terrifying solo paddle across the lake with a large swell and gusts of wind that would blow me backwards. Fortunately they relented, I made it across, and wind conditions generally did not get too much worse. Occupied B, then looked for A again- still no luck! We found X relatively easily, then decided to run up to the fault core outcrop in Hokuri Creek for samples and real geology.
Alpine Fault fault core at Hokuri Creek
Endlessly fascinating saponite gouge textures
Day 3. With a great deal of luck (first rock I overturned!) I found A, the last of our 6 lost monuments. We occupied A (thanks to the digger battery the builders lent us!), then setup X with the other GPS. The rain began at 11am and continued through the day. With spare time while we were waiting on the GPS, and too much rain for productive fieldwork, we decided to try packrafting down Hokuri Creek. The approach was surprisingly easy along the true left bank, which also gave us a view of all the major obstacles including several significant drops and holes. This was going to be an interesting run!
We didn't have wetsuits, only rain gear, so I was pretty motivated to avoid a full drenching and stay upright. We hiked up to just above the main confluence, the logical place to put-in. The run was surprisingly fast and fun with some excellent features and little flat water! There were three particular obstacles of note: (1) a series of rapidfire drops in a long and sustained stretch of river, (2) a steep and messy chute-like rapid near the Alpine Fault outcrops, and (3) a sustained wave-train immediately under the three-wire bridge. We both had a clean and enjoyable ride straight through (Class II-III+) and slid right into the lake, where we paddled back to Hokuri Hut.
Gearing up for the first descent of Hokuri Creek (Class II to IV-)
Day 4. More rain today. We removed the GPS from A and had a cup of tea with the builders before moving on. We arrived at X a little early so took a walk along the beach to the old Jamestown site, where an ill-conceived idea to put in a settlement was master planned by folks in England with little founding in reality. We moved the GPS down to reoccupy Z (this time with a functional battery) and then retreated to Hokuri Hut. It was raining very hard by the afternoon! We had some visitors to Hokuri Hut. I was pretty content to stay dry and read my book but Jeff had other ideas. Eventually he succeeded in convincing me to have another run down Hokuri Creek (this time it would be at much higher flow). What a fast run this time! It was probably Class III- to IV- at this flow. The drops on the upper portion of the run were all probably a bit more straightforward this time and the wave trains were much more fun at this flow. Once we got to the bend in the river near the Alpine Fault things got crazy. Here we wanted to stay hard right but I was slow with my positioning and ended up too far left to make the main channel. Jeff stayed right and had a wild ride down some messy holes which eventually flipped him. Over to the left in no man's land I was having a bit of a panic- the river on this side dropped over large boulders and past grabby logs in flow about twice the width of my packraft. I pretty much could only anticipate clearing one obstacle at a time- reaction, reaction, repeat, action, reaction, repeat. To my great surprise I managed to clear the rapid unscathed (looking back at it I have no idea how). I was feeling a little shaken up but glad to still be upright and intact as I waited for Jeff. I was soon to get my turn though. The wire bridge rapids were looking considerably beefier. I chose a line right of center clipped the edge of a hole and flipped instantly. I executed a pretty effective self-rescue considering it was my first kayak flip ever, managing to herd my packraft, paddle, and hat through several more wave trains until I got to shallows and could right myself. Thoroughly drenched in water and adrenaline, I was remarkably warm. We floated the last cruisy stretch to the lake, and onward for a peaceful paddle back to the hut just before dark. The trampers (some of which went to extraordinary lengths to keep their feet dry) thought us rather peculiar showing up to the hut like wet dogs.
A calm crossing for a change
Walking towards Jamestown
Hokuri Creek ?first descent?
The aftermath
The last day we picked up the last GPS from station Z (this time still recording) and packed up. The whirlibird dropped out of the sky more-or-less on time and off we went. Amazingly we managed to find all six needles in the haystack that is the thick bush of Fiordland. Now its only qa matter of processing the data to see what the results are. Preliminary results suggested the GPS had poor signal due to the thick bush overhead, but more careful attempts are forthcoming. I would love to have a convincing answer one way or the other.
Photos of me by Jeff. Thanks to him! Thanks also due to the fine people at Hollyford Track Ltd. who have always been friendly towards research in the valley.
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