The combination of climate change and increased urbanization has resulted in cities with no historic flooding experience suddenly vulnerable to extreme flood events. Climate change increases the frequency and intensity of rainfalls, whereas urbanization decreases the total porous surface area, resulting in pluvial (rainwater) flooding. One such affected city is Valkenburg, located in South Limburg in the Netherlands. Valkenburg flooded on 14 July 2021 after experiencing an unusually heavy rainfall that deposited 146 mm of rain into the Geul Catchment, causing up to €600 million in damage. In such communities, flood early warning systems (FEWS) are emerging as possible non-structural solutions to minimizing costs of damage and loss of life from flooding. These systems are people-centered, end-to-end networks that predict floods before they are meant to occur to warn people living in vulnerable areas so that they can protect their homes, businesses, and themselves. 
The FEWS network for the Geul uses forecasted precipitation data to predict discharge and water level conditions for the Geul. In the event that the predictions result in an abnormally high water level, warnings can be communicated to the necessary parties and to the population to allow for ample preparation. At the time of the July 2021 flood, the system was offline, with experts familiar with the network believing that it would not have worked even if it was online. This project aimed to analyze the existing FEWS from data collection to communication of warnings to locate existing issues and potential sources of weakness, thereby improving the system to effectively warn for future floods. 
Each step of the FEWS was tested to find and strengthen potential weaknesses. The data inputs were analyzed and compared to the recorded precipitation that occurred in July 2021. Then, this data was inputted into the FEWS prediction models to understand how the system would have calculated the discharge and water level for that event. Both the July 2021 flood event as well as four non-flooding scenarios (summer storm, winter storm, dry season, wet season) were tested. The models were then used to create a flood map, and this flood map was inputted into the Damage and Casualties Model (SSM2017) to estimate how much in damage costs could be saved for the case with FEWS and the case without FEWS. Communication and evacuation were not extensively tested in this research project due to these components being determined by social and political frameworks. 
When inputting the precipitation data associated with the July 2021 flood, it was found that the 1D model overestimated the water level to be 76.5 m+NAP, 6.5 m greater than the expected water level. Implementing a 2D grid reduced this value to 70 m+NAP, which matched the expected water level. It was also found that both HBV and SOBEK produce simulation results that consistently do not align with recorded data, suggesting a need to recalibrate the models to better reflect the behavior of the Geul River. Analyzing the recorded discharge and precipitation data found that using forecasted precipitation data gives Valkenburg enough time to communicate warnings and evacuate if necessary. Cost-benefit analysis that compared the economic impact of warning versus not warning revealed that warning and evacuation is more cost-effective than not not warning and evacuating, even in the case of a false alarm. An evacuation in the event of a false alarm can cost 1/10 of the difference in damage costs with and without evacuation. However, false alarms must still be avoided, as they erode trust in the warning system, thereby reducing its effectiveness in possible cost and loss of life reduction. Analysis of the expected costs of damage with and without the warning system revealed that the inclusion of the warning system has the potential to reduce the total expected damage by more than 50%. 
The insights found in this project can be used to improve the FEWS for the Geul. Future research can be done to create a 2D or quasi-2D model that can predict the discharge and water levels of the Geul in a timely manner (no more than one-two hours’ simulation time). The 2D aspect is important to a warning system as the expected amount of water affects how the community prepares for the disaster. This project can contribute not only to the improvement of the FEWS for the Geul but also for the improvement or creation of FEWS for other river catchments in newly vulnerable cities. ... Read more

The city of Venice has been prone to flooding throughout its history. However, flooding has recently been occurring more often than before. As a result, engineers have collaborated to come up with a potential solution to the flooding. This solution, a mobile barrier known as the Experimental Electromechanical Module (Modulo Sperimentale Elettromeccanico, or Mo.S.E.) has been in progress for quite some time now and is therefore still not functional. On 12 November 2019, an extreme high water level event occurredwith the second highest recorded water level in history. The flooding event should have been prevented by the construction by a flap gate storm surge barrier, a project started after the 1966 historical high water event, which takes the name of Mo.S.E. project. In this paper, the 2019 event is analyzed, investigating the causes of the event and the design criteria of the Mo.S.E. barrier project in terms of its structure, construction process and completion state at the time of the event.The meteorological and hydrological causes of the 12 November 2019 is studied to better understand what caused the event. If the causes of an event are understood, a solution to similar future events can be more easily determined. Historic waterlevel data is used to better understand the hydraulic conditions within the Venice Lagoon. Existing research projects that utilized similar data are studied to estimate the return periods considered in the design of the Mo.S.E. barrier. The return period for the 12 November event (187 cm) was found to be about 130 –140 years. The return period for the water level at which the Mo.S.E. barrier is designed to be fully closed (110 cm) is 5 –7 years. The effects of climate change and subsequent eustacy are also analyzed to determine how this would affect the return periods of both the 12 November 2019 event and the barrier closure level. Analysis of estimated future return period data predicted thatthe return period range for the 12 November event would decrease from 130 –140 years to50 –100 years while the return period range for the Mo.S.E. barrier closure would decrease from 5 –7 years to 2 –5 years. An estimation of the flooded buildings and roads is made. Surface elevation data is compared with the water level of the November 2019 flood event. In this way information is gained about what areas were flooded. By using downloaded from Open Street Maps, information about all buildings and roads, including their location, are obtained. Analyzing this data results in information about what buildings and roads are flooded. These results, together with numbers of damage per flooded object, are used to make an estimation of the total direct damage due to the flood event. The estimated total direct damage amounts to €870 million.The estimated damage to cultural heritage amounts to €244 million. Also, the case was investigated in which the Mo.S.E. barrier would have been operational during the November 2019 flood event. If the barrier had closed, the total direct damage would have been€257 million.Conclusively, an analysis of the management system of the Riequilibrio E Ambiente (REA, Lit. Rebalance and Environment) mega-project and the Mo.S.E. project is conducted to visualize the main failures and delay causes which lead to the circumstances of incompletion of the barrier at the time of the 2019 flood event. Through a careful analysis of the main events and technical problems encountered throughout the planning and construction of the barrier, the leading cause of delay is found to be political corruption, along with uncareful definition of project objectives and extreme levels of project complexity. Currently, the completion of the storm surge barrier is scheduled to be at the end of 2021. In 2019, the construction of the barrier wasfound to be completed at its 94%, signifying an 8-year delay past the original completion date of 2012, which was determined at the begging of the construction works in 2005. The Mo.S.E. barrier project is merely one part of a much larger mega-project designed for the safeguard of Venice which was meant to be completed in 1985. While the Mo.S.E. barrier is delayed almost 8 years, the entire project is delayed by a total of 26 years.It is recommended to direct further researches to future impact, considering climate change, and the amount of damage for certain return periods and the impact of the Mo.S.E. barrier on this last. Hence data collection making damage estimations more accurate, internal corruption prevention and management within large infrastructure works and feasible optimizations solutions to apply to the Mo.S.E. barrier in order to face sea level ris ... Read more