Case Studies

Surveying a Curved Weir : Precision Tactics

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The Background

Date: September 2024

As September crept in, Storm were tasked with surveying the River Kennet and some of its tributaries to produce an accurate and comprehensive channel survey. Their client, were looking to expand a water treatment site that had suffered with flooding in the past. The geospatial data was required to create a hydraulic model of the area surrounding the site which would inform decisions on construction. The project, offered a few interesting challenges to the team of Storm surveyors.

Process

The Challenge

The depth of the river in the Kennet Canal meant that wading through it was not an option. With the help of an engine powered boat and advanced survey equipment (Trimble’s R12i), surveyors were able to navigate the watercourse safely while collecting accurate data. However, the most technically demanding aspect of this job was capturing a curved weir/ bridge structure on a section of the river. The projection of a curved structure on a 2D face is tricky to visualise and therefore to survey on site. To overcome this, the team used precise tape measurements to ensure that key features, like tunnel length and distance between abutments, were accurately represented in the final drawings without distortion.

The weir was steep and hazardous to cross, but fortunately, a footbridge directly above it provided the surveyors with safe access. When surveying the fish pass attached to the weir, extra caution was required due to the damp concrete. To minimise the risk of slipping, surveyors held onto the handrail and wore strapped helmets at all times while they were not on the footbridge.

Process

The Results

The importance of preparation that is required before deployment to site can take place (also known as the desktop study) is often underrated. For this particular project, a significant number of landowners had to be contacted to arrange access to their land for survey to take place. To access the canal required a permit from the Canal and River Trust. This level of preparation was essential to the success of the project to keep it on it’s critical path.