The increasing demand for stream restoration projects in the Netherlands, driven by legislation, prompted interest in more integrated approaches. TAUW (Technische Adviesbureau van Unie Waterschappen) and WSAM (Waterboard Aa and Maas) collaborated on stream restoration measures for the Lage Raam stream in the Raamvallei, initially using a 1-dimensional model. However, questions arose regarding the suitability of a 2D model for this project.

This research explored the applicability and potential of a 2D hydrological model made in Tygron to provide new insights and outputs for this stream restoration project, including inundation maps, water level fluctuations, and evaluating designed restoration measures. Simultaneously, the study assessed Tygron's applicability for large water systems in the Netherlands by evaluating its underlying settings and parameters.

In the first part of this research, the study demarcated stream restoration measures for the Lage Raam, focusing on redesigning the stream to enhance nature-friendly banks. The Tygron water module was introduced, emphasizing critical simulation setup adjustments such as the rainfall overlay and simulation settings investigated in the initial testcase study. The settings investigated in the testcase were: 'Water level to shorelines', 'Waterline reconstruction', 'Angle stabilizers for partly flooded cells', 'Manning value', 'Grid cell size', and 'Grid/stream placement'.

Results from part 1 indicated that among the six settings tested, only three significantly influenced water level simulations in channels. Variations in Manning values demonstrated a pronounced effect on water height accuracy, with lower values correlating with better simulation outcomes in the testcase. The influence of Manning values was more pronounced in narrower streams, where shallower water depth worsened inaccuracies in the model's backwater effect. Notably, Grid cell size and Grid/stream placement were crucial for achieving accurate outcomes. The optimal grid cell size was found to be 1 by 1 meter or of higher resolution. Additionally, aligning streams parallel to grid cells generally improved results, although the influence of grid placement diminished with increased grid cell count per channel.

The second part introduced the study area, the 'Raamvallei', for case studies 2 and 3, outlining designs for cross sections with swamp areas as restoration measures. Case study 2 validated the Tygron model using measured data from the Raamvallei obtained from WSAM and rain events, testing its suitability and model setup for water systems. Case study 3 implemented TAUW's restoration design to evaluate Tygron's effectiveness of these measures.

The results in part 2 showed that evaluation in a larger watershed scenario (Raamvallei) underscored the model's robustness when configured for extensive water systems. Grid cell size sensitivity analysis highlighted the optimal range (1m x 1m or smaller), lower resolutions causing water loss in the Lage Raam water system, underscoring the resolution’s impact on modeling outcomes. Achieving accurate connectivity between primary, secondary, and tertiary waterways was crucial, requiring iterative adjustments including culvert generation and hydraulic structure calibration. The third case study highlighted challenges in data retrieval and storage due to Tygron's limitations in exporting detailed simulation data over time. However, it also demonstrated Tygron's capability in simulating level fluctuations and flow rates, despite challenges in data analysis.

In conclusion, Tygron was capable of using the explicit Saint-Venant scheme to calculate 2D shallow water equations where it accurately simulated a complex large water system in the Netherlands. Additionally, it could be used for projects such as the Lage Raam to provide insights into stream restoration designs. However, for a model to be successfully used and have results that could be easily understood, some settings were important to look at and some changes in data collection were needed. Future research should encompass diverse test cases to validate Tygron's performance across various scenarios and compare it with other 2D hydrological models for broader applicability insights.

Based on the study's findings, several recommendations were proposed to enhance Tygron's utility in hydrological modeling. These included exploring new data storage approaches to handle extensive datasets more efficiently, optimizing the use of limit areas to simplify model complexity without compromising simulation accuracy, and improving connectivity tools like the culvert generator for seamless integration with external data sources.