Hydraulic modelling to enhance resilience at Titchwell Marsh

The challenge

Titchwell Marsh, a vital coastal wetland on the Norfolk coast, is internationally recognised for its ecological importance, particularly as a habitat for migratory birds. The site is increasingly threatened by tidal erosion, particularly around the Volunteer Marsh and Parrinder Bank, where an engineered breach in the embankment has altered tidal flow patterns.

Key concerns included:

• Erosion Risk: Accelerated tidal flows were contributing to erosion of the Parrinder Bank and widening of the breach in the Volunteer Marsh.
• Habitat Protection: The freshwater lagoon and surrounding marshes are critical for biodiversity and require careful hydrodynamic management.
• Data Gaps: Limited real-time measurement data necessitated a robust modelling approach to understand flow dynamics.

The solution

Haskoning developed a high-resolution 2D hydraulic model using the 3Di modelling platform, focusing on simulating tidal flow behaviour under three distinct scenarios:

• Scenario A: A typical high tide event.
• Scenario B: An elevated tidal wave (T1).
• Scenario C: The December 2013 storm surge, one of the most severe in recent history.

The model incorporated:

• LiDAR-derived Digital Terrain Models (1m² resolution) for accurate topography.
• Dynamic friction mapping based on land-use and topographic elevation.
• Sub-grid modelling to capture fine-scale flow dynamics within a computationally efficient framework.

A sensitivity analysis was conducted to test the impact of varying bed friction values, and video-based validation using RSPB field observations helped confirm model accuracy. Model result animations were presented to the client team, enabling them to sense check the model and improve confidence.