Setting Out and Monitoring During the Repairs of the Collapsed Kew Riverside Walk Embankment
- TopoCrew Team
- Nov 6
- 3 min read
Project Snapshot
Client: FM Conway
Project Type: Topographical Survey, Movement Monitoring, Setting Out
Sector: Flood defence, Recreational
Location: Richmond, London
Surveying Accuracy: up to 2 mm
Technology Used: Leica RTC360 (Static Laser Scanner); Leica TS15 & GS15 (Robotic Total Station & GNSS)
Survey Area: ca. 3000 sq. metres
Objectives
In October 2024, an approximately 20-metre section of the historical towpath, dating back to the 18th century and now known as the Kew Riverside Walk, collapsed due to erosion caused by continuous tidal movements. TopoCrew was commissioned to provide the critical surveying support during the repair works. As part of the project we have:
established a survey reference point network
carried out a topographical survey using laser scanners and total stations
provided regular movement monitoring reports
set out positions and monitored piling operations
set up satellite-controlled excavator
provided as built surveys
The topographical survey included not only the area immediately affected by the collapse but also a 1-kilometre section of the footpath’s crown to identify high and low spots.
Once the construction phase commenced, our team was responsible for setting out the new piling and culvert installation. In addition to these setting-out tasks, our team also carried out weekly monitoring routines and daily checks of the Kew-side retaining wall during the piling phase.
Preparation
A local survey network was established on site by traversing the required survey area, with GNSS observations taken at key locations for georeferencing. Once the network was calculated and appropriately adjusted in MicroSurvey Star*Net, we used our Leica RTC360 scanner to capture the breach area in high detail. The resulting point cloud was then processed in the PCS application to extract a vectorized digital model. The footway was measured using a traditional total station, and the results were integrated into the final topographical drawings.
Challenges and Solutions
The tidal nature of the River Thames posed a major challenge during the works. Site visits had to be synchronised with low tide so that the bottom of the work area became accessible. The piling works, however, had to be synchronised with high tides, as the piling hammer was operated from a barge on the River Thames.
Aside from the logistical challenges, the most significant difficulty we faced was ensuring the accuracy of the piling works. The 15-ton hammers were operated from a barge that had to remain afloat at all times to avoid excessive tilting, which could only be safely achieved during the highest tides. Continuous monitoring of the sheet piles was required to ensure proper interlocking and compliance with design specifications. In some cases, buried obstructions caused significant deviations from verticality, and achieving the correct position required a second attempt.
Despite these challenges, successfully overcoming them was highly rewarding, as reflected in the quality of the project’s final outcome.
Maintaining the continuity of the monitoring scheme proved to be both difficult and complex. The retaining wall, a brick structure, had to be monitored to prevent a sudden collapse during the construction works. GMP104 monitoring prisms were installed along the upper part of the wall; however, over time, they became too dirty from tidal wash to allow accurate readings. Cleaning them was not always possible due to restricted access and safety constraints.
The integrity of the bricks used in the retaining wall had degraded over the decades, and some of the prisms were even dislodged by floating debris constantly striking the wall during high tides. We soon realised that the widely accepted and commonly used method would not be feasible in this case. As a result, the decision was made to use reflectorless measurements instead of prisms. This raised the question of how to maintain continuity in the observation series.
Fortunately, we have scanned the entire wall section prior to the commencement of construction works, allowing the original positions of the observation points to be traced and movement accurately shown.
For the riverbed rehabilitation works, the 3D riverbed model has been uploaded to the satellite-controlled excavator and we have set up the system to enable precise automated operation.
Results and Project Impact
Despite challenging tidal conditions and structural instability, the team successfully delivered precise topographical data and maintained construction accuracy utilising advanced surveying methods, including GNSS, total station, and 3D laser scanning. When traditional monitoring techniques failed due to environmental constraints, we adapted by implementing reflectorless measurements and utilising pre-construction scans to ensure continuity and reliability.
The much-loved Kew Riverside Walk will soon be fully restored and reopened for everyone to enjoy once again.
This project is a great example of how TopoCrew supports challenging projects from start to finish: from laser scanning and topographical surveying to setting out, movement monitoring, machine control and as built documentation.
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