Project Snapshot
| Category | Details |
| Client | Northwest Hydraulic Consultants (NHC) |
| Project Name | Pattullo Bridge Replacement Hydraulic Model Surveying |
| Location | Fraser River, British Columbia |
| Date | Ongoing since 2020 |
| Resource | Pattullo Bridge Replacement Project |
Project Overview
Introduction
As part of the Pattullo Bridge Replacement Project, Northwest Hydraulic Consultants (NHC) constructed a 1:80 scale model of the Fraser River, including the SkyTrain, CN Rail, and Pattullo bridge pilings. This model is used to test the hydraulic behavior of the proposed bridge design and upgrades under various flow scenarios.
Project Challenges
The model needed to precisely reflect real-world riverbed conditions to provide reliable hydraulic data. Ongoing scans were required after each simulated test, capturing even the smallest shifts in riverbed contours under controlled flood conditions.
Underhill’s Approach
Underhill first performed a high-accuracy 3D laser scan of the original riverbed model to capture as-is conditions. Following each hydraulic test, our team scanned the model again, aligning each scan using fixed targets placed around the facility. These datasets were transformed into digital surface models and compared with the baseline to visualize changes in sedimentation and erosion caused by proposed bridge structures and water flow.
For over four years, Underhill has provided consistent scan-to-scan comparisons that help engineers evaluate how new bridge designs and seismic upgrades will interact with river dynamics.
Notable Outcomes
- High-resolution data to support bridge design and seismic upgrade decisions
- Repeatable scan overlays delivering visual and measurable changes
- Precise alignment methods for reliable change detection
- Enhanced understanding of hydraulic behavior under varied environmental conditions
Project impact
Underhill’s precise 3D scanning of the Fraser River scale model allowed NHC to track riverbed changes and assess hydraulic impacts of the new bridge design. The repeatable scan data supported safer, data-driven decisions for both bridge replacement and seismic upgrades. This project demonstrated Underhill’s value as a reliable geospatial partner on complex infrastructure modeling.
