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Development of a systematic approach to include the spatial information of point measurements.

Het spoorviaduct door Delft is een bron van ergernis voor omwonenden door de enorme geluidsoverlast en doordat het viaduct een visuele en fysieke barri is dwars door de stad. De gemeente Delft is daarom een politieke lobby gestart om het viaduct te vervangen door een spoortunnel. Daarbij zal de ruimte boven de tunnel opnieuw ingericht worden. In de plannen van de gemeente is er op de tunnel bebouwing geplaatst. Het doel van het onderzoek is te bepalen of de bebouwing op de tunnel beperkt wordt door het risico van explosies in de tunnel of andersom. Een complicerende factor bij het ontwerp en gebruik van de tunnel is dat het tracoor Delft gebruikt wordt voor het vervoer van gevaarlijke stoffen. Indien de gevaarlijke stof vrijkomt, bestaat er het gevaar van een explosie. Dit kunnen gaswolkexplosies of BLEVEs zijn. In mijn afstudeeronderzoek heb ik in eerste instantie bepaald wat de kans op een explosie is. Vervolgens is bepaald wat de maximale explosiebelasting is die de tunnel op kan nemen. Hierbij is gebruik gemaakt van het ontwerp van de tunnel zoals dat door de betrokken partijen nu is opgesteld. In een volgende stap zijn de gevolgen voor de bebouwing op, naast en over de tunnel bepaald. Deze gevolgen zijn getoetst aan de externe risiconormen en uit de beschouwing blijkt, dat de tunnel met geplande bebouwing erop voldoet aan de externe veiligheidsnormen. Tot slot is er nog een analyse gedaan naar de mogelijk te nemen maatregelen om de kans op en de gevolgen van een explosie te verkleinen.

In 2008 kwam de tweede Deltacommissie met het voorstel om het waterpeil van het IJsselmeer in de toekomst met 1,5 m te verhogen. Door de verwachte zeespiegelstijging zal het namelijk steeds moeilijker worden om het overtollige water van het IJsselmeer af te voeren naar zee. Om dit onder vrij verval te kunnen blijven doen is een peilopzet noodzakelijk, met ingrijpende dijkverhogingen tot gevolg. In dit afstudeeronderzoek zijn een aantal alternatieve maatregelen onderzocht, waarmee in een betere beheersing van het IJsselmeerpeil kan worden voorzien. Op deze manier kan grootschalige dijkverhoging wellicht worden voorkomen. Het afstudeeronderzoek spitst zich toe op twee zgn.“Alternatieve Beheersmaatregelen” waarmee, tijdens en voorafgaande aan een hoogwater op het IJsselmeer, het peil kan worden verlaagd. 1. Reduceren van de IJsselafvoer met behulp van een nieuw regelwerk in de Pannerdensche Kop; 2. Vergroten van de uitstroom door tijdens extreem hoog water in het IJsselmeer, het Markermeer (incidenteel) als Noodbuffer in te zetten. Naast deze alternatieve beheersmaatregelen is tevens gekeken naar de optie van bemaling via de Afsluitdijk. Hiervoor is, op basis van het meest extreme klimaatscenario volgens het KNMI, een schatting gemaakt van de maximaal benodigde pompcapaciteit bij verschillende combinaties met beheersmaatregelen. Daarnaast zijn ook globaal de (pomp)kosten berekent om het huidige peil in de toekomst te kunnen handhaven.

After Hurricane Katrina the Bring New Orleans Back committee advised to use the Gentilly Ridge to split the Orleans Metro Bowl into compartments in order to reduce the consequences of a flood. The Gentilly Ridge is a natural sand elevation (ridge) of approximately 0,50 1,00 meter NAVD88 in the OMB landscape. The objective of this thesis is to determine the cost-effectiveness (risk reduction versus construction costs) of compartmentation of the Orleans Metro Bowl (OMB) in comparison with an improvement of the primary levee system. Three alternative compartment levees are compared with one primary system improvement. In this thesis the total flood risk of the OMB has been represented in two scenarios: the Katrina event (hurricane class III) and a hurricane class IV event. - The Katrina event is the complete scenario of the Katrina disaster of August 29, 2005. The probability of the event is set to be 1/50 per year. - A hurricane category IV event. The probability of the event is set to be 1/200 per year. Once the probability (in probability/year) and the consequences (in $) of a scenario and alternative have been determined the risk (in $/year) is known. This risk is calculated to a Net Present Value ($) to compare with the costs of a alternative ($). With a detailed cross-section of the compartment levees a calculation of the heightening costs of an earthen levee for each compartment trace has been made. Compartment levee 3 appeared to be less cost-effective than the levee improvement and drop-out. An boundary optimal design level for compartment levee 1 and 2 is calculated and appeared to be both 1,50 meter NAVD88. To overcome a disaster like Katrina, a compartment levee alone will not suffice, therefore the cost effectiveness of a combination Levee improvement and compartment levee is elaborated. Compartment levee 1 (1,50 meter NAVD88) is a quick and cost effective way to deduct the total risk for economical damage in the OMB for the short term. Once the total primary system has been improved, a compartment levee (trace 1) is still of economical value.

In the southeast of the city of New Orleans, in St. Bernard Parish lies a coastal defensive area, which is formed by a primary dike, a secondary dike and a transitory wetland area in the middle. During Hurricane Katrina on the 29th of August 2005, a huge storm surge from the east overtopped and destroyed large sections of the primary dike. The surge continued through the wetland overtopping the secondary dikes and flooded large parts of St. Bernard Parish. The flooding killed over a hundred people and made many homeless. The coastal defensive system at St. Bernard Parish is very well comparable with the concept of ComCoast COMbined functions in coastal defence zones. This is a European project, which develops and demonstrates alternative solutions for flood protection in coastal areas. One of its main solutions is to use a wide coastal defence zone, containing a transitional area between an overtopping resistant primary dike and a lower protective secondary dike. The transitional zone will be a buffer for the storm surge and will be an area suitable for multipurpose use, with great opportunities for both man and nature. This Master Thesis analyses the failure of the St. Bernard Parish coastal defence system. Subsequently, it develops spatial integrated solutions for the coastal defence zone, using the coastal defensive strategies, which follow from the ComCoast-concept. Additionally, the effects of wetlands on a storm surge are investigated by means of an analytical analysis and a numerical model. It was concluded that catastrophic failure of the coastal defence system could have been prevented if the primary dike was not partly constructed of poorly non cohesive materials. Some basic constructional calculations and a quick study on environmental impacts made clear that the ComCoast alternatives; Overtopping resistant dike and Foreshore recharge, offer the most suitable solutions for the St. Bernard Parish area. The study on the effect of wetlands on a storm surge showed that it can both lead to a decrease, as an increase of the eventual storm surge height at the dike. The analytical and numerical approach has increased the understanding of the hydraulic behaviour of the system.

In the Netherlands 6,8% of the total electricity production came from renewable energy sources. Electricity was 17 % of the total energy consumption in that year. In total 1,2% of the energy consumption was therefore renewable. The objective of the cabinet to get 20% of the energy from renewable energy sources will therefore be a major challenge. All available means should therefore be employed to reach this objective. Tidal energy did not seem feasible for the Netherlands, as the tidal difference is relatively small. After research done for a tidal power plant at the Brouwersdam it turned out that production of tidal energy could become attractive when combined with other social interests, such as improving the ecology of the area. On the 11th of March 2005 the Netherlands signed an agreement about the Western Schelt. This agreement said that Hertogin Hedwigepolder should be given back to the estuary. This had to be done to compensate nature loss due to deepening of the Western Scheldt as a result of shipping requirements. By combining the desire of the cabinet for more energy production from renewable energy sources with the plans to compensate for nature loss in the Western Scheldt the idea came to gain tidal energy from polders. Because of this new function of the polder it is called the energy polder. The aim of this study is to research the economical and technical feasibility of a tidal power plant along the Western Scheldt. The attention in this study lays on the design of the structures needed for the tidal power plant. With this design a good insight in the costs is obtained. A design, a hydraulic model and an economic model were made to obtain insight in the cost benefit ratio. It turned out that the energy price needed for this plan is equal to that of offshore wind energy.

Multilayered Safety (MLS) is seen as the next step in Dutch flood risk management. In the last decades the idea that only flood defenses can prevent floods gave way to the realization prevention can also be implemented along other lines, e.g. giving the rivers more space. The next thought was that next to preventing floods it should be possible to reduce the loss due to flooding. Therefore, MLS is meant to introduce comprehensive flood risk management by implementing three layers, or put differently safety nets: 1. Prevention (dikes, space for rivers, etc.), 2. Spatial Solutions (flood-proofing houses, elevating houses, re-locating etc.), 3. Crisis Management (evacuation, warning, etc.). Before this study, there was no academic interpretation of MLS and it had never been tested comprehensively. Consequently, a theoretical framework is being developed in this thesis to be able to model MLS. This is followed by a hypothetical case study and additional one for the City of Dordrecht to examine the actual effect of MLS on the flood risk and its cost-efficiency. It was found that theoretically MLS is indeed an alternative to only Prevention. Furthermore, it introduces the option to better customize flood risk management to local circumstances. By doing so, flood risk management becomes more cost-efficient. As the cost-efficiency is found to be dependent on the initial safety level, it is concluded that in the Netherlands MLS only has the potential to supplement the existing flood protection. In areas with a heavy implementation of flood defenses like in Dordrecht, MLS is fit to complement flood risk management rather than replacing the prevailing Prevention approach. However, to do so (local) authorities need to be able to base their flood management policies on flood risk, e.g. by benchmarking a certain Individual Risk.