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Network Rail Bathymetry survey River Calder

Whalley Viaduct Following on from the initial successful 3D terrestrial scans of Whalley Viaduct. Network Rail requested an additional Bathymetry survey of the river bed, to investigate any potential issues. The Whalley arches are important components of this busy railway route built between 1846 and 1850. One feature of the viaduct is that it not only traverses land for much of its length, but also crosses the river Calder. Bathymetry To ensure the viaducts integrity in the river Calder section,  a bathymetry survey was undertaken. A 100m section of the river was mapped using a HyDrone RCV remote control survey  platform. The HyDrone RCV was connected to a GNSS receiver. Adding the GNSS receiver, enables points on the river bed to be accurately geo-located. Using the data from the GNSS assists with the building a 3D model of the river. In addition, the receiver was linked with a LIDAR survey of the riverbanks to enable the accurate profile build of the river under the viaduct.  Monitoring erosion and scour Monitoring the riverbed around the structures is a critical undertaking. The principal mode of viaduct base failure is typically focused on the area where flooding and scour occurs. Flooding, climate change and increase of rainfall significantly change river hydraulics and, in some cases, it can cause serious problems to the base of structures. This survey concentrated on riverbed scour, identified using our high-resolution sonar bathymetric remote-control boat. Data Collection Using our bathymetric underwater surveying technology gives our engineers the ability to inspect water retention and riverbed features using specialist software back at our base. The data we collected from the watercourse characterises the river both above and below the waterline at the River Calder location. Additionally, we visualised the impact of objects affecting river flow and evaluated the changes in the river caused by sediment dynamics. The comprehensive bathymetric data captured the above features with a precise resolution and detail. Consequently, the inspection and assessment of the viaduct features and improved sonar detail increased the evaluation of the watercourse. Thus, ensuring safety of the structure by identifying any areas of concern. The models provided will be used to assess future maintenance requirements and to ascertain any immediate works required. 

Scanning with Network Rail – Scans, drones and viaduct arches

Whalley viaduct built in 1846 stretches across the river Calder. The viaduct is a magnificent structure, consisting of 49 brick arches, 620m long and 21.3m high. Locally the area is known the Whalley Arches. Traditionally, the surveying and inspection of these structures would be undertaken manually, with measurements and repetitive paper-based data entry. The traditional method is both time consuming and expensive; requiring extensive scaffolding. To eliminate the human errors attached to traditional surveying, and to save on time, we employ terrestrial 3D laser scanning techniques to capture buildings and structure data. Combined with photography of the structure, the laser scan data assists in assessments, helping with the prioritisation of maintenance issues,which may or maynot be required. Our team travelled to Whalley Arches late in the evening, our job was to scan the top railway section at midnight, the best time to work when scanning railways - whilst trains were stopped. However, due to strong wind gusts and torrential rain, the night time scan was cancelled much to our dismay. Undeterred, the next morning, clear skies and a mild breeze greeted us as we set off with a RIEGL scanner, two drones and camera team to capture the arches. Several areas under the arches required cleaning out of saplings, brambles and general discarded waste. These were cleared by the ever helpful team from Network Rail, armed with Chainsaws, and industrial hedge trimmers. As soon as these obstacles were cleared, giving us line of sight for the scanner and operator and easier access to the grounds, our job commenced. Each arch was scanned with terrestrial lidar, which made for some interesting scrambling up embankments and into residents gardens to ensure a clear view of the arches for the scanner. Thanks to all the residents who allowed us into their property, who were all very kind and welcoming. A total of 187 scan positions, combined with 3,000 high resolution photographs gave us a highly detailed accurate comprehensive analysis of the complete structure.