Delta Flood Management Study

Project Highlights

The Corporation of Delta retained KWL to undertake a major flood management study to examine two types of flood scenarios:

• regional flooding across Delta resulting from a dyke breach in river and sea dykes, and
• local flooding in East Delta resulting from frequent to rare rain events.

The flood management study investigated both types of flooding using computer hydraulic simulation models, paired with geo-spatial analytical tools.  The study quantifies the hazard associated with a number of flood events for both flood scenarios, and provides potential approaches to address flood concerns through upgrades to infrastructure or through land-use planning.

An extensive drainage system survey was completed to inventory the ditches, culverts, and hydraulic structures for input into a database and into a hydraulic model.  A SWMM hydrologic model was built to generate rainfall-runoff flow hydrographs that were used by the MIKE11 hydraulic model to simulate flows, velocities, and water levels in the lowlands.

The models were validated using the Corporation’s SCADA data for discharge pump operation and spot water level measurements taken during large events in 2001 and 2003.  The MIKE11 DAMBREAK module was used to simulate dyke breaches in the sea dykes and the Fraser River dykes.  The results of the dyke breach models can be used to update the flood construction levels required for the Delta lowlands.

The inclusion of two major flood mechanisms made this a complex and unusual study and provided valuable results for assessing flood hazard risk for the Corporation.