Improving the sea defense of Central Termoeléctrica Antonio Guiteras Multi-Disciplinary Project, 2020 Document : Improving the sea defense of Central Thermo Electrico Antonio Guiteras Place and date : Havana, January 2020 Authors : Robin van den Berg : Matthijs Buijs : Tjerk Krijger : Alexandra Rijnink : Wessel Vrijmoeth University : Delft University of Technology Faculty : Faculty of Civil Engineering & Geosciences Department : Hydraulic Engineering Supervisors TU Delft : Dr. Robert Lanzafame, Dr. Olivier Hoes CUJAE : Prof. dr. ir. Luis Fermín Córdova López Cover photo: Satellite image of hurricane Irma on September 8, 2017 at 8:00 a.m. (UTC -6:00) (NOAA, 2017) Sponsors Delft Deltas, Infrastructures & Mobility Initiative (DIMI) Universiteitsfonds Delft Waterbouwfonds Delft (not a logo available) Universities Polytechnic José Antonio Echeverria Delft University of Technology (Ciudad Universitaria José Antonio Echeverría) 2 3 Preface This report is the result of a throughout study executed by five Civil Engineering students from the Technical University of Delft. A part of the master program is doing a project with students from different master disciplines. This project is performed by students from the Hydraulic Engineering and Water management disciplines. The goal of the project was to improve the sea defense in front of the Central Thermo Electrico Antonio Guiteras. This powerplant is situated in the province Matanzas, close to the capital of Cuba. To experience civil engineering in Cuba and obtain information directly from the source, the project team was situated in Havana. For a little more than two months the project was executed at Universidad Tecnológica de la Habana José Antonio Echeverría (CUJAE). Here prof. dr. ir. L. F. Córdova López was to our everyday availability to answer all our questions. We want to thank him for his excellent guidance throughout the whole project. Furthermore, we want to thank the people who helped us back in The Netherlands; our supervisors Dr. Robert Lanzafame, and Dr. Olivier Hoes. A special thanks to Chris Lashley who was of great help with our XBeach model. We would also like to thank Deltares for supplying us with the Delft3D license. We have learned a lot from this project. A running Delft3D and XBeach model was created and a final solution which meets our requirements was designed. Next to this, we had a great experience in Cuba. Robin van den Berg, Matthijs Buijs, Tjerk Krijger, Alexandra Rijnink, Wessel Vrijmoeth Havana, January 2020 4 Abstract The central Thermo Electrico Antonio Guiteras (CTE Antonio Guiteras) is a thermoelectric power plant located in the bay of Matanzas. In 2017, hurricane Irma passed the north coast of Cuba and destroyed the primary sea defense in front of the CTE, causing major damage to the plant. The power plant is renovated, and a new and improved sea defense is currently being constructed. Before Irma, the coastal defense consisted of a wall parallel to the coastline. The wall was made of multiple impermeable rectangular concrete blocks, placed on a seal. The blocks were not anchored to the seal. During Irma the blocks were displaced and severally damaged. The new sea defense is designed by the Cuban engineering and architecture company EMPAI. The design consists of a concrete wall with a steep slope and a bullnose on top. It has a tooth-shaped anchorage to prevent the wall from sliding. Instead of reinforcement steel the wall is strengthened by carbon fiber strings. The wall can be divided in four sections: sections A-1, A-2, B and C. The sections differ in orientation and height. Section B and C are situated further away from the coastline and section C has a berm in front of the wall. The goal of this report is to answer the following question: to what extend is the power plant protected during extreme weather conditions and what improvements are needed to ensure that the power plant can remain operational during these extreme weather conditions? First it needs to be determined which extreme weather events are of importance in the scope of this project. Two extreme weather events occur in Cuba; cold fronts and tropical cyclones. Cold fronts generate maximum wind speeds corresponding to a category 3 tropical cyclone, meaning that a category 5 cyclone like Irma can generate wind speeds that are much higher than those of a cold front. Cold fronts have a higher probability of occurrence, but since the coastline of the CTE is located perpendicular to the North-East, waves generated by cold fronts have little influence on the project site. Hence, only tropical cyclones are assessed in this report. To determine what the hydrodynamic and meteorological effects are of this extreme weather event, a synthetic tropical cyclone is created. This synthetic hurricane must generate large significant waves in combination with a big storm surge, to have severe impact on the CTE. It must also have a significant probability of occurrence. To determine this normative synthetic hurricane, multiple synthetic hurricanes are simulated in Delft3D and XBeach and their corresponding return period is determined. As Irma significantly damaged the CTE, this hurricane is taken as the basis for all synthetic hurricane combinations. The hurricanes each vary from Irma in maximum wind velocities, forward speeds and their tracks. To set up a reliable Delft3D model, first hurricane Irma is simulated and iteratively validated with actual recorded data. To simulate the physics of hurricane Irma, a spiderweb grid is created at the locations of the hourly best track of Irma. The grid has a radius of 600 kilometers around the eye of the hurricane. This spiderweb grid is loaded into a Matlab script, which gives as output a spiderweb grid with for each grid point a pressure value, a wind speed value and a wind direction, all calculated according to the Holland formula. This is then used in the Delft3D model as input for the pressure and wind fields of the hurricane. The hurricanes follow one of the following two tracks; Irma’s hourly best track or Irma’s hourly best track shifted 1.5 degrees latitude to the North. During the period of 31st of August 2017 06:00 till the 11th of September 2017 12:00 Irma was classified as a TC. This period of six days is simulated with time steps of 10 minutes. Prior to this period of six days, the hurricane is pinned at the border of the Delft3D grid for two days together with a uniform wind over the entire grid, to simulate a fully developed sea state. The output of the Delft3D model is validated with recorded data of observations stations in the Gulf of Mexico. Recorded water levels and wind speeds of buoys near Key West are used for validation. Additionally, wave heights of buoys in the middle of the sea, quite far away from the CTE, are used. XBeach is used to simulate the nearshore physical processes. XBeach can more accurately predict wave propagation and includes higher order processes in its simulation. As input for the XBeach model, the output of the Delft3D model is used. 5 After running all the synthetic hurricanes in Delft3D, the five resulting normative hurricanes are run in XBeach. The synthetic hurricane that creates the largest significant wave heights at the project area is taken as a basis for the final design. It has a return period of 1580 years. This combination has very high wind speeds with peak gusts of 80 m/s, a low forward speed of 3 m/s and follows Irma’s track on the north side of Cuba, close to the shore of the CTE. This hurricane gives a maximum significant wave height of 8.8 m with a corresponding storm surge of 1.61 m at the location of the CTE. The mean significant wave height is 6.49 m with a standard deviation of 0.92 m during a period of 3.5 hours. With these values a research on the current defense wall is done. This study shows that sections A-1, A-2 and B all have an unacceptable failure probability due to overtopping if the modeled normative synthetic hurricane would occur. Section C also shows an unacceptable failure probability but is less under-designed than the other sections. For all sections, adjustments to the current design need to be made. Section A-2 also contains an inlet channel for cooling water, this proves to be a difficult element in the design. In normal conditions an open channel to sea does not provide a problem, during a storm however large amounts of water can flood in and the defense wall can be damaged at this location. To improve the existing design, several alternatives are possible for each function of the sea defense. Four functionalities can be distinguished and will be discussed separately. These are; wave reduction, barrier, gap protection and drainage capacity. The first is wave reduction, which will cause waves to lose part of their height and consequently create less impact. The best way to improve this is by placing a pile screen on the foreshore. The second function is the barrier directly in front of the CTE. This is meant to stop the waves and limit overtopping. In this situation a seawall is the most suitable option. The slope can be adjusted, and design of the wall can be optimized to influence the overtopping. To improve the existing sea defense, a solution needs to be sought for the inlet channel. The solution must allow the continuous flow of water but must provide more safety against flooding during an extreme storm condition. The option examined to protect the gap is to construct higher walls around the channel and basin. Improving the drainage of the area of the power plant gives the advantage that water that enters as either precipitation, overtopping or overflow can be discharged and hence make sure that vital parts of the power plant are not flooded.