{"id":7980,"date":"2020-11-13T08:34:53","date_gmt":"2020-11-13T07:34:53","guid":{"rendered":"https:\/\/www.ebroresilience.com\/avance-del-proyecto\/estudios_detalle\/ebro-in-cabanas-de-ebro\/"},"modified":"2023-08-21T10:26:28","modified_gmt":"2023-08-21T08:26:28","slug":"ebro-in-cabanas-de-ebro","status":"publish","type":"estudios_detalle","link":"https:\/\/www.ebroresilience.com\/en\/avance-del-proyecto\/estudios_detalle\/ebro-in-cabanas-de-ebro\/","title":{"rendered":"Ebro in Caba\u00f1as de Ebro"},"content":{"rendered":"\n
Download Detail Study – Section 8 (PDF)<\/a><\/div>\n\n\n\n

Background<\/strong><\/h3>\n\n\n\n

Caba\u00f1as de Ebro is located on the banks of the Ebro, on the outside of a large meander. Historically, the Ebro flooded the meander located in front of the town, so that the waters did not reach great height or speed. <\/p>\n\n\n

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\"Figure
Figure 1. Recreation of a flood of the Ebro river in Caba\u00f1as de Ebro on the aerial photograph of 1927 (own elaboration).<\/figcaption><\/figure>\n<\/div>\n\n\n

During the 1960s to 1990s, the Ebro River flood defense dykes were built. In the case of the town of Caba\u00f1as de Ebro, the defenses of the upstream section of the town are shaped in the form of a funnel (see figure 2), so that the flowing waters are forced to travel the entire perimeter of the meander, which means passing in front of the defenses of the urban center.<\/p>\n\n\n

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Figure 2. Configuration of the current defenses (in yellow) around the town of Caba\u00f1as de Ebro (own elaboration).<\/figcaption><\/figure>\n<\/div>\n\n\n

This circumstance favors overflows towards the outer part of the meander, by increasing the height of the circulating waters, and increases the erosion processes in the bed of the riverbed in this area, where the urban center is located.<\/p>\n\n\n\n

To mitigate these effects, the town’s defenses have been gradually reinforced with the construction of breakwaters, walls and defense dikes, which have been reinforced or rebuilt after each flood event.<\/p>\n\n\n

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\"Figure
Figure 3. Reinforcement of the protection wall of the urban area with stone (Eduardo Berian Luna).<\/figcaption><\/figure>\n<\/div>\n\n\n

Following the major floods of 2015, the west defense dike of the town center was reinforced, the perimeter defense of the meander in front of the town was lowered and a relief channel (artificial river arm that comes into operation during floods) was built to reduce the amount of water flowing in front of the town’s defenses.<\/p>\n\n\n

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Figure 4. Actions carried out after the 2015 floods (Confederaci\u00f3n Hidrogr\u00e1fica del Ebro).<\/figcaption><\/figure>\n<\/div>\n\n\n

A population security perimeter was delimited in 2017. This safety perimeter consists of the delimitation of the defense structures of the urban core, their leveling, their preparation to be able to carry out emergency works with guaranteed safety and the construction of a system of milestones marked with a scale, which serve to control the levels of the avenue and help in monitoring its evolution and decision making.<\/p>\n\n\n

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Figure 5. Caba\u00f1as de Ebro security perimeter (Ebro Hydrographic Confederation).<\/figcaption><\/figure>\n<\/div>\n\n\n

Similarly, after the 2018 flood, the main defense wall of the urban area was reinforced and part of the breakwater (a structure made up of large stone blocks) protecting the wall, which had been lost, was replaced.<\/p>\n\n\n

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Figure 6. Actions carried out after the flood of 2018 (Confederaci\u00f3n Hidrogr\u00e1fica del Ebro).<\/figcaption><\/figure>\n<\/div>\n\n\n

At present and after these interventions, Caba\u00f1as de Ebro is protected for floods with a return period (average time it takes for a flood of similar flow) of 10 years, according to the hydraulic studies carried out.<\/p>\n\n\n\n

On the other hand, a similar phenomenon occurs in the meander located between Caba\u00f1as de Ebro and the bridge over the Ebro on the A-126 road from Alag\u00f3n to Tudela. In this case, the defense dikes around the perimeter of the meander could not be fully consolidated and are in a different state of preservation. However, recent floods have increased the erosive processes on the outer bank of the meander and it is likely that in the short term the integrity of the VP-24 road, from Alag\u00f3n to Gallur, will be endangered as it passes by this point.<\/p>\n\n\n

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\"Figure
Figure 7. Erosion at the apex of the meander. Behind, the VP-24 highway (Eduardo Berian Luna).<\/figcaption><\/figure>\n<\/div>\n\n\n

Objectives of the study<\/strong><\/h3>\n\n\n\n

Within the scope of the Ebro Resilience Strategy, a total of 260 kilometers of the Ebro River are being studied, divided into 15 sections.<\/p>\n\n\n\n

Section 8 is centered in the town of Caba\u00f1as de Ebro and covers the 4 km of the riverbed before the town and the 4 km after, approximately, ending at the A-126 road bridge over the Ebro River.<\/p>\n\n\n\n

The specific objectives of the study were as follows:<\/p>\n\n\n\n

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  • Evaluate the level of protection of the urban area of Caba\u00f1as de Ebro for floods with a return period of 25 years and propose actions to prevent flooding, should it occur.<\/li>\n\n\n\n
  • Analyze the erosion processes of the local defenses and propose actions to reduce them in the event that these processes are observed.<\/li>\n\n\n\n
  • Reduce the likelihood of damage to the VP-24 highway. <\/li>\n\n\n\n
  • Reduce the risk of flooding in non-urban areas by reducing the speed at which water flows and\/or the height that floods reach over fields.<\/li>\n<\/ul>\n\n\n\n

    Work performed<\/strong><\/h3>\n\n\n\n

    The analysis of the digital terrain model has shown that the defenses around the perimeter of the meanders have caused the channel bed to deepen as it passes through these defenses and that, by forcing the water to make the entire perimeter of the meander, the channel has been strongly eroded at the toe of the meanders.<\/p>\n\n\n\n

    The described effect is more pronounced near the town of Caba\u00f1as de Ebro, where a pool with an average depth of 15 meters has been generated in front of the defenses of the urban center (Figure 8).<\/p>\n\n\n

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    \"Figure
    Figure 8. Topography of the riverbed obtained in the area next to the urban center (own elaboration).<\/figcaption><\/figure>\n<\/div>\n\n
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    \"Figure
    Figure 9. Fragment of the digital terrain model (own elaboration).<\/figcaption><\/figure>\n<\/div>\n\n\n

    Once the hydraulic model has been configured and calibrated, the target flood is reproduced, in this case the one corresponding to a return period of 25 years, which is equivalent to a flow of 3,100 m3\/s<\/sup> in this section, and the effects produced are analyzed.<\/p>\n\n\n\n