University of Twente Student Theses

Towards a more natural and robust regional water system in an agriculture dominated area : scenario analysis for the side watercourses of the Groenlose Slinge to increase water retention and decrease peak discharges

Pfeijffer, C. (2021) Towards a more natural and robust regional water system in an agriculture dominated area : scenario analysis for the side watercourses of the Groenlose Slinge to increase water retention and decrease peak discharges.

PDF
24MB

Abstract:	This research addresses the drought problems in the area of the Groenlose Slinge. The Groenlose Slinge is part of the Berkel located in the Eastern part of the Netherlands. To solve the drought problems in the area the water system of the Groenlose Slinge and the whole water system of the Berkel has to be changed. The dry summers cause the groundwater levels to decrease to critically low levels. However, the amount of the peak precipitation events increase during the winter. The necessity of solving these problems are in line with Kaderrichtlijn Water (KRW) criteria. The aim of this research is to design, model and evaluate various scenarios for the side watercourses of the Groenlose Slinge to achieve a more natural and robust water system. To achieve the research aim, six interventions for the side watercourses of the Groenlose Slinge are identified and afterwards translated into three scenarios of which each contains one type of the following measures: natural measures (scenario 1), water retention measures (scenario 2), and technical measures (scenario 3). Scenario 1 aims to achieve a more natural and robust water system, scenario 2 aims to increase retention in the area and scenario 3 contains technical measures that are derived from current drought mitigation measures and are intensified. The designed scenarios will all be modelled in SOBEK Rural 2.13, compared with the modelled current situation and afterwards evaluated via a multi-criteria analysis. This will lead to the most suitable scenario for the study area. The difference in discharges, water levels, water depth, flow velocity, and freeboard levels compared to the current situation will be calculated. Afterwards, the scenarios are evaluated against each other based on flood safety, ecology, water retention, and required space. The average freeboard levels next to the watercourses of the current situation is during the winter 45 centimeters and the summer around 48 centimeters. The freeboard levels of scenario 1 are comparable to the freeboard levels of the current situation. However, the freeboard decreases slightly during the dry months and increases slightly during wetter periods. Scenario 1, natural measures, retains 1.5% of the total discharge more than the current situation. The freeboard levels of scenario 2, retention area measures, are also similar to the current situation, the average freeboard during the spring and winter is increased by a maximum of 0.5 centimeters. The discharge during the summer is decreased by 3.3% and during the spring by 9.75%. This scenario also leads to an increase of groundwater levels of an average of 48 millimeters throughout the study area. The average freeboard of scenario 3 is decreased by 20 centimeters during the whole year. During the summer 3.8% of the discharge is retained in the area. From the multi-criteria analysis, it follows that scenario 2 comes out as the best scenario for the area. In this scenario, the largest amount of water is retained in the area over the year while maintaining flood safety in the area. After carrying out an elaboration for a specific watercourse, it was found that this watercourse performs the best with the implementation of scenario 1. From this, it can be concluded that scenario 2 is the overall best scenario, although scenario 1 can be better for specific watercourses hence this has to be further researched. The implementation locations of the various measures could have been expanded. In this research, the area was divided into three areas: valley, transition area and plateau. To get a better understanding of the effects of a scenario, the area should be divided into more area types and more measurement locations need to be used. In this way, the effectiveness of a measure on a certain area type can be found. Next to this, more in-depth research to scenario 1, natural measures, should be performed. Scenario 1 has improvement opportunities and potential. The main potential of scenario 1 is in the way cross-sections are shaped and for which return periods the cross-sections are designed. By adjusting these two things scenario 1 can be fine-tuned. For follow-up research, the scenario preference of each watercourse should be researched. Each watercourse differs and every watercourse has a different optimal solution. This research discusses the approach to side watercourses of the Groenlose Slinge. Research should be performed to improve the current Groenlose Slinge into a more natural and robust water system.
Item Type:	Essay (Bachelor)
Faculty:	ET: Engineering Technology
Programme:	Civil Engineering BSc (56952)
Link to this item:	https://purl.utwente.nl/essays/87700
Export this item as:	BibTeX EndNote HTML Citation Reference Manager

Show download statistics for this publication

Repository Staff Only: item control page