Development and Calibration Challenges for a Large Confined Drainage System Model

This presentation gives an overview of the process, challenges, and lessons learned for drainage model development and calibration for the Vancouver International Airport (YVR). YVR is located on Sea Island, at the mouth of the Fraser River, and most of which is at or near sea level. As a result, the island is protected by a full perimeter dike. An extensive confined drainage system has been developed to convey the storm runoff towards outfalls through the perimeter flood protection.

The objective of this modelling project is to assist Vancouver Airport Authority (VAA) with an understanding of how the drainage system performs under existing and anticipated future conditions, including climate change and sea level rise, to support decision-making related to management, maintenance, operation, and upgrades. To achieve this, KWL developed a comprehensive 1D/2D drainage model of the entirety of Sea Island using PCSWMM. The model includes a rain-on-grid hydrological component, a 1D network of the drainage conveyance system (e.g., pipes, ditches, pumps), and a 2D surface to capture overland flow and surface ponding.

Model calibration was challenging due to its large size and 2D mesh resolution, as well as having multiple points of calibration. A high resolution 2D mesh, relative to the model size, was needed to adequately represent water levels near airport infrastructure in the flat terrain. To overcome these challenges, calibration was performed in multiple stages using KWL’s internal machine-learning-calibration tool (Parallax) and various sensitivity analysis scenarios.

Development of the YVR drainage model provided a detailed modelling experience with innovative troubleshooting ideas, emphasized the importance and challenges of obtaining accurate data, and tested the limitations of GIS tools and SWMM-based modelling software.

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