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Evaluation of the excavation of the spillways in the dikes along the Linge and Waal in case of an inundation of dike ring 43
Janse, Stijn van (2025) Evaluation of the excavation of the spillways in the dikes along the Linge and Waal in case of an inundation of dike ring 43.
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| Abstract: | The Netherlands famously is a low-lying country at the mouth of several Europe’s largest rivers. But due to the low elevation of the country, river floods have always posed a threat. As much as 29 percent of the country is at risk from flooding of the major rivers (Planbureau voor de Leefomgeving, 2024). The Dutch doctrine to protect the low-lying areas from floodings from both rivers and the sea revolves around dividing the low-lying areas into so-called dike rings. Each dike ring is a section of low lying area surrounded and protected by primary flood defences (such as dikes, weirs and dunes) and higher lying terrain. As the Rhine enters the Netherlands it splits into several different branches. The two main branches are formed by the Nederrijn and its continuation the Lek in the north and the Waal in the south. In between these branches two middle-sized dike rings are located: dike ring 43 upstream and dike ring 16 downstream. The border between the two dike rings is formed by a dry dike called the Diefdijk. The Diefdijk protects the downstream dike ring 16 in case that the upstream dike ring 43 is inundated. In between the Nederrijn and the Waal flows the Linge, a small river that lies completely within dike rings 16 and 43. The dikes along the Linge are lower than the dikes running along the Nederrijn and Waal and do not form a part of the primary flood defences protecting dike rings 16 and 43 from the large rivers. The dikes along the Linge do however provide an extra barrier if the upstream dike ring 43 is inundated. To help to alleviate the load on the Diefdijk during an inundation of dike ring 43, the Lingewerken are constructed. The Lingewerken consist of a series of spillways in the dikes of the rivers Linge and Waal. If in the case of an inundation the water level in dike ring 43 is higher than in the Waal, the spillways of the Lingewerken can be activated to guide flood water from dike ring 43 (back) into the Waal. While research from the 1990s has shown the positive effect of the Lingewerken on the safety of dike ring 16, little research has been conducted about the effect of the Lingewerken on dike ring 43. Also, the effect of the Lingewerken has only been quantified in terms of a water level reduction, but not in terms of damage and casualties. The research objective of the project is to evaluate for which flood scenarios of dike ring 43 it is advantageous to use the Lingewerken in order to prevent as many casualties and as much economic damage as possible. The research is conducted by integrating the Lingewerken in the latest flood model of dike ring 43 of Waterboard Rivierenland, utilising D-HYDRO software. The subsequently found effect of the Lingewerken on the flood water level is then evaluated by using the Schade- en Slachtoffer Module (translated: Damage and Victims Module) to find the expected reduction in economic damage and amount of casualties. The effect of the Lingewerken on preventing damage and casualties is evaluated for two different dike breach events. The first evaluation assesses the benefit of the spillways along the Waal and the Linge for a very severe inundation scenario (return period 1/10000 years) with a dike breach location south of Tiel. It is found that in case of a large scale inundation of dike ring 43, excavation of the spillways along the Waal reduces the size of the inundation considerably. The amount of damage and casualties is significantly lower by excavating the spillways along the Waal. On the other hand, excavation of the spillways along the Linge in addition to the spillways along the Waal has a limited effect. By excavating the spillways along the Linge, the spread of the inundation is accelerated but the size of the inundation stays more or less the same. The second evaluation is conducted to answer whether or not it is beneficial to excavate the spillways along the Linge and the Waal if there is a smaller-sized inundation from the north near Beusichem (return period 1/100 years). In a scenario without utilisation of the spillways, the dikes along the Linge form a barrier for the inundation to spread further causing significant water levels north of the Linge but low water levels south of the Linge. By excavating the spillways in the dikes along the Linge and, the water levels north of the Linge are reduced but the inundation spreads further south before leaving the dike ring through the spillways along the Waal. It is found that when the spillways are excavated, the decrease in damage and amount of victims north of the Linge does not weigh up to the extra damage and casualties south of the Linge. Excavation of the spillways along the Waal and Linge is therefore disadvantageous in case of a smaller-sized inundation from the north. It can be concluded that for both assessed flood events, a severe flood coming from the south of Tiel and a less severe flood from the north near Beusichem, disadvantageous to excavate the Linge spillways as the excavation of the Linge spillways leads to more casualties and economic damage. On the other hand, it is certainly advantageous to excavate the Waal spillways in case of a large scale flood south of the Linge in order to reduce the damage and amount of casualties significantly. A conclusion that the usage of the Linge spillways is disadvantageous for every flood scenario might however be premature based on only two investigated dike breach scenarios. A scenario not investigated where the Linge spillways could prove to be useful is in case of a large scale inundation north of the Linge from the Nederrijn. Excavation of the Linge spillways in addition the Waal spillways could provide a quick way for the flood water to leave dike ring 43 thereby reducing the size of the inundation. Therefore the recommendation is made to investigate the effect of the spillways along the Linge for a large scale inundation from Nederrijn before drawing definitive conclusions about the Linge spillways. |
| Item Type: | Essay (Bachelor) |
| Faculty: | ET: Engineering Technology |
| Programme: | Civil Engineering BSc (56952) |
| Link to this item: | https://purl.utwente.nl/essays/106054 |
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