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.
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.
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.