Follow our progress on this frequently updated blog ... or should we say, updated when we have nothing better to do ;-)
In the early hours of 22 March, an intense period of rainfall passed across Westland with considerable spill over the Main Divide. In Glenorchy we were woken by a loud thunderstorm and the Rees Catchment received a considerable amount of rainfall. Just before dawn the flow peaked at over 250 cumecs at the Invincible Gauging Station.
Today we have been gauging the flow at the State Highway Bridge, as the flood recedes. We have gauged at 70, 60, 45 and 30 cumecs. We have also taken to the skies and taken aerial photos of the inundation extent.
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Inundation of the study area. Taken mid-afternoon, when flow
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A chute, with Mt Earnslaw in the background.
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On 7 April, we will giving a talk on our work, our technology and our findings to date. The talk will be held in the Glenorchy Cafe. The talk will take place at 7.30pm and is free. Warming soup and bread will be available before the talk, at 6.45pm. Tickets for food are available from the GYC.
For further information, click here (pdf document, approx 1MB).
We have just finished another scan of the Rees River study area. Over the last seven days we have scanned at 231 scan stations. Richard is now busy working up the results to produce a Digital Elevation Model.
Following the hydrological event at the beginning of March, there has been a significant amount of sediment transport and morphological change in the study reach. A sixth scan of the study reach has therefore been started. High pressure is arriving over the next few days, so hopefully scanning conditions will be good for up to a week.
A low pressure system passed along the West Coast of South Island, delivering considerable spillover into the Rees catchment. The Rees water level reached a peak of almost 1400mm at the Invincible gauge board. This is the biggest event that we have had since mid-January!
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Inundation! Looking downstream from the upstream
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Looking upstream from the downstream end of
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Aerial photos have been taken to complement the scan data that has recently been collected. A river channel bathymetry survey has also been undertaken.
There was another reasonably small hydrological event on 24 February. Richard and Becky have been gauging the flow and bedload transport rate beneath the State Highway Bridge.
A gravel mining company has begun operations to extract material from the Rees floodplain. The volume of material extracted from the study reach will be surveyed to ensure that it is accounted for in the reach sediment budget.
Becky and Richard have begun the fifth scan of the river reach. Windy conditions are making it particularly difficult to keep the scanner in a horizontal position whilst data is collected!
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Scanning the centre of the study reach.
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Unified data from the fifth scan. This image is constructed
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Following a small hydrological event on 13 February, Richard, Damia and Jose went into the field to recover both painted patch and RFID tracers. The team also undertook a number of Grain Size Distribution surveys. These surveys involved measuring the a,b and c axes of 100 pebbles in a 2m by 2m quadrat. The data from these surveys will be used to calculate statistics to characterise surface roughness, which will then be compared to information extracted from the terrestrial lidar scans.
Becky has produced around 150 additional tracer pebbles with RFID chips in them. These are being released into shallow channels in the middle of the study reach. Hopefully we will be able to recover the position of each of these tracer pebbles after each hydrological event over the next few months. In total, 395 tracers have now been “released” into the study reach.
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Freshly painted pebbles. Every pebbles contains one RFID chips.
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A line of "released" RFID tracer pebbles.
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A number of 1m by 1m gravel patches are being spray painted in a bright colour before every high flow event. Typically patches are being sprayed at bar heads and bar tails. After each high flow event, we are trying to recover as many coloured stones as possible, recording their location and their size. This will provide us with data to estimate how far sediment moves with each event.
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A "yellow" bar head patch. The photo looks downstream.
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A "green" bar head patch. The photo looks upstream.
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Richard has recently been applying terrestrial laser scanning to the Fox Glacier on the West Coast of South Island. He joined Duncan Quincy, of the Aberystwyth University’s Centre for Glaciology, and Jordan Herrmann, from Maptek, for the ten-day project.
The team used Maptek’s I-Site 4400 scanner to survey the glacier terminus. The scans were taken from four positions, located approximately 100 metres from the calving front, distributed from the true left to the true right of the valley. The glacier terminus was scanned every day, for ten days. A number of ablation stakes were also installed on the surface of the glacier, close to the terminus. Every day the position of each stake was surveyed using a Leica Real-Time Kinematic (RTK) GPS system. The ablation rate at each stake was also measured.
It is hoped that the scan data, together with the ablation stake measurements and meteorological data, will provide insight into the nature of advance, melt and collapse at the glacier terminus.
James, Becky and Mark have just completed the fourth survey of the study reach. The scan is the most detailed yet, encompassing 314 scan stations. This equates to approximately five billion survey points. In addition to the scanning, aerial photographs have been taken and a bathymetric survey of the study reach has been completed.
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A typical point cloud from a scan station. Each individual point
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A mosaic of the aerial photographs. Data will be extracted from
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On the evening of Boxing Day, water levels at the Invincible gauging station reached approximately 1800mm (above the gauge datum). This compares with a baseflow level of approximately 500mm. At the State Highway Bridge, the channel that conveys most of the flow has switched from the right bank to the left bank.
During November around 100 tracer pebbles were “released” into the river. Each tracer pebble has an RFID chip located in it. Hopefully we will find these pebbles after each event to estimate how far each pebble is moving during each event. Today, a further 150 pebbles were “released”.
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Recording the position of each tracer pebble.
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Searching for “lost” tracer pebbles with an antenna: |
The third scan of the study area is now complete. This scan was interrupted by a “small” high flow event, resulting in the need to scan the floodplain in two-sections, with a reasonable degree of overlap between each section.
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Looking upstream along the study reach.
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High winds on 17 December picked up mica and deposited it on everything, |
All the scan data from the first scan of the river has now been georeferenced and merged together to produce a Digital Terrain Model of the study area. This Digital Terrain Model shows ground levels as observed from the laser scanning. Further editing will be required to remove erroneous data, such as tripods, vegetation and the all terrain vehicle.
Scan data density (left) and Digital Terrain Model (right).
Since the ReesScan team arrived in New Zealand they have been eagerly looking forward to the first time that the floodplain would be covered by a sea of water. Today, their Christmas present arrived early. At Invincible, a peak discharge of approximately 250cumecs (metres cubed per second) was measured. At the state highway bridge, the river filled the floodplain from the left bank to the right bank.
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A flow of approximately 250cumecs rushes through
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NIWA gauge peak discharge. |
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Bank to bank flow at the State Highway Bridge.
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Sediment rich river water from the Rees mix with |
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Gauging flow from the State Highway Bridge.
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Flow recedes at the State Highway Bridge |
Two additional water level gauges have been installed. One has been positioned at the old Rees River fording point, which is approximately five kilometres upstream of the State Highway Bridge. This gauge will help to estimate water levels at the upstream end of the study area, which will be useful when modelling floodplain flows. The second gauge has been positioned on Oxburn. This is the only major tributary between the Invincible Gauge and the State Highway Bridge Gauges. Therefore gauging flow on this tributary will help to close the water budget for the study area.
James, Damia, Ramon, Becky and Richard took to the skies in an Alpine Chopper to take aerial photos of the study area. The depth of water will be estimated by correlating the “blueness” of the water in the photos with calibration data from a bathymetric survey.
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Glenorchy Airport. Probably the only airport in the world
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Looking upstream towards the study area. |
After a succession of three high flow events, the second scan of the study area has begun.
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Scanning on the floodplain as cloud spills
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The study area (red outline) seen from a helicopter. |
For the first time during the project we have had a reasonable amount of rain in the headwaters of the Rees catchment. River levels rose by just under a metre at the Invincible gauging station, where flow was gauged and water samples were taken. Damia will be measuring the suspended sediment content of these samples when he visits NIWA’s laboratories in Christchurch.
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The gauging cableway at Invincible, looking upstream.
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The gauging cableway at Invincible, looking downstream. |
Measuring bedload transport rates: 19 November 2009
Regular surveying of the floodplain topography following each high flow event provides information on ground level change between events. It does not, however, provide information on the amount of sediment that has moved through the system during the event. To close the study areas sediment budget it is necessary to estimate how much sediment is moving through the system. To achieve this a Sontek S5 Acoustic Doppler Current Profiler is being used.
The S5 measures the position of the Current Profiler using differential GPS (accurate to sub-cm spatial resolution) and bottom tracking. In simple terms, if the river bed is stationary (i.e. no bedload sediment transport is occurring) then the GPS and bottom tracking positions should be identical. However, if the river bed is moving (i.e. bedload sediment transport is occurring) then the GPS and bottom tracking positions will be different. This difference can provide information on the rate that the bed is moving, and by inference the amount of bedload transport that is occurring.
A series of experiments are being undertaken over the next few weeks to calibrate the S5 so that it can be used to estimate bedload transport rates.
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Colin Rennie holding a Helly-Smith bedload
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The calibration is taking place at relatively low flows |
Over the next couple of weeks Murray Hicks, Ramon Batalla and Colin Rennie will be visiting the catchment. During this time we will focusing upon installing a turbidity meter at Invincible, setting up an automatic water sampler at Invincible and calibrating an acoustic Doppler Current Profiler to measure bedload transport.
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The team visited Muddy Creek, a tributary of the Rees that is located
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 The team walked from Muddy Creek to the State Highway Bridge to |
Nesting birds: Saturday 21 November 2009
The gravels of the braided Rees River provide grounds for a number of nesting birds. To date we have seen black-fronted terns, dotterels, wrybills and pied oystercatchers on the floodplain. We’re taking care to minimise the time we spend surveying in nesting areas to minimise disturbance. A brief summary of bird life on New Zealand's braided rivers can be found in a Department of Conservation leaflet.
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The banded dotterel (Charadrius bicinctus), or Pohowera, measures
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The banded dotterel often chooses nesting sites on high bars with no vegetation. Typically three eggs are laid in a shallow scrape. The eggs |
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When disturbed dotterels leave their nests, spreading their wings
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Pied oystercatchers (Haematopus ostralegus finschi), or torea, measures about 46 centimetres and weighs about 550 grams. Pied oystercatchers migrate from beaches and estuaries in early spring, nesting on open riverbeds or farmland. When their nests are approached oystercatchers fly into the air and then dive towards the disturbance. |
Tuesday 10 November 2009
A long time since our last update. We've been taking full opportunity of the good spring weather! During this time we've completed a first full scan of the study reach ... incorporating over 5,000,000,000 survey points. These have been georeferenced to the new NZ mapping system, with a mean error of < 1 cm in xyz; not bad for earth scientists! A quick first shot of the registered point cloud (much reduced in scale) is shown below.
 3d point-cloud obtained from ArgoScan near the Paradise Road bridge. The colour scaling is based on the intensity of laser reflections, with bright gravels showing higher returns than dark, wet sandy facies.
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This snapshot from Leica Geosystems Cyclone software shows a highly decimated, relief shaded, image of our first reach scale point cloud ... the full version contains over 5 billion survey observations! The data are generated from more than 300 individual scans and are georeferenced using a combination of on-board navigation and GPS mobile targets. |
We've also been turning our hand to completing the installation of the gauging stations and constructing a rating curve for the gauge at Invincible. A lot of practice with cableways, reels and small boats which the images below allude to! The live data stream from the Invincible station is now available on this website.
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Damia and Becky get to grips deploying the S5 from the slackline cableway at Invincible. The flow here is a miserable 15 cumecs, we are hoping for more than 10x this in a significant event.
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 The Sontek S5 aDcp River Surveyor: this four beam acoustic velocity profiler measures 3d velocity vectors in bins as small as 10 cm as it is pulled across the river. Position is measured using an advanced bottom tracking estimate derived from the four beams or directly by GPS. |
Lastly, we have also installed our ReesCams ... timelapse recording cameras supplied by NZ firm Mi5 security. These record images at the gauging stations every 5 mins and provide a solid visual check on all the electronics.
This time-lapse animation was acquired over five days at the Paradise Road gauging station. The images provide crucial visual data on the river level we also record digitally at our monitoring stations and can help us understand the link between river level and inundation area on the braidplain.
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Time-lapse recording from 04-09 November 2009 at Paradise Road Bridge.  |
The Argo is taken to the reach for the first time and tested across the gravel bar (and in channel) terrain...
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... and the careful art of loading the argo onto the trailer is rehearsed.
Saturday 17 October 2009 Lee Pimble provides the ReesScan team with training in the use of Sontek's River Surveyor S5 to gauge flow at the Rees River Invincible Gauging Station.  Thursday 15 October 2009 Work has started to gather pebbles for the radio particle tracking. Approximately 500 pebbles are being collected from the gravel bed. Each pebble will be tagged with an RFID chip and then re-introduced into the river. After each high flow event the positions of each radio tagged pebble will (hopefully) be recovered.  Wednesday 15 October 2009 Mick Sievers and Lee Pimble from Sontek are visiting to install a side-looking Argonaut at the River Rees Invincible Gauge. Lee will also be providing the team with guidance in the use of Sontek's River Surveyor and will be training the team in the use of Sontek's suite of software.   Tuesday 13 October 2009 Work installing a network of eight benchmarks around the Rees River study reach begins. These will consist of nails drilled into large boulders (right bank) and ground marks (left bank).    Friday 9 October 2009 James and Damia join Richard and Becky at the ReesScan project field base in Glenorchy, South Island. Around a ton of air freight arrives at the same time! The weather station is the first piece of equipment to be assembled in the front garden and correctly tells us that it's sunny!   NIWA have completed installation of the River Rees Invincible Gauge. This consists of a pressure transducer with telemetry and a cableway for rating. Later in the project a Sontek side-looking Argonaut will be installed to gather information for velocity indexing.
Mid-September 2009 The Argo mounted scanning system is going through it's final paces of testing by Aberystwyth University's Intelligent Robotics Group before being air freighted to New Zealand.
 August 2009
New ReesScan blog to be launched soon to keep you up to date with project as we ready for departure to NZ later this summer!
August 2009
Richard Williams and Becky Goodsell appointed to ReesScan project team! Richard joins the team from JBA Consulting, and Becky from positions at the NZ Department of Conservation and NZ Ski.
July 2009
New research positions available! Closing date 30th June 2009!
July 2009
Hear more about ReesScan and our research using terrestrial laser scanning at the IAG 7th International Conference on Geomorphology in Melbourne, Australia (July 2009)
March 2009
ReesScan team together with collaborators in the Robotics Group at Aberystwyth develop a new robotic mobile laser scanning system (March 2009) |
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