Case study:Inturia dam removal

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Location: 43° 7' 10.39" N, 1° 56' 25.71" W

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Project overview

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Status	Complete
Project web site
Themes	Environmental flows and water resources, Habitat and biodiversity, Hydropower
Country	Spain
Main contact forename	Rincón Sanz
Main contact surname	Gonzalo
Main contact user ID
Contact organisation
Contact organisation web site
Partner organisations
Parent multi-site project
This is a parent project encompassing the following projects	No

Stages of the Inturia dam Removal. The image shows the comparison with the initial state and the results of the first two stages of the project and also the reduced height in each year. Photo credits: Irekia.

Project summary

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The Inturia dam was removed in four stages due to the size of its infrastructure and the large volume of sediment accumulated in its reservoir. A staged demolition is more natural since it involves a gradual restoration of the solid flow regime. In each performance, 3 meters high are removed from the wall of the dam.

Before the first demolition stage, the useful volume of the dam was estimated at 70,500 m3 as the sediments had filled the dam. The flooded area of the reservoir was between 38,000 and 40,000 m2. The three existing drains placed in the bottom of the dam did not work.

The pre-demolition works was aimed to protect the Bertxin dam, located downstream, from the released sediments. In addition, it was proceeded to partly emptying the dammed area by gradually opening the bottom drainage.

The removal works of the Inturia dam lasted four years, one for each stage of the project. In this way, the changes that have occurred in the river between stages can be evaluated. The actions were performed in summer when the flow is low, except in the stage 4 that was done in January.

The reservoir accumulated about 236,000 m3 of sediment. The river mobilized about 60,000 m3 in each stage.

In order to start the works, it is necessary to first make a land access to reach the river. Approximately 300 m3 of material was used to make these roads. This material was removed after the work and was re-used in the following stage of the removal process (a year before).

After the last phase, a path was made along the right side to allow fishermen access to the river. Finally, a viewpoint has been created where a plaque has been placed with photos and data explaining the process and the importance of this removal.

Monitoring surveys and results

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A monitoring process was developed before the first stage of the removal. Bathymetries were first performed in the reservoir to determine the amount of sediment accumulated.

Two geomorphological monitoring reports were made. The first one, carried out in 2013, was a morphological characterization in the study section (upstream and downstream of the dam) prior to the first stage of the removal. Following the first stage, two monitoring campaigns were carried out (September 2013 and April-June 2014). Besides, a second monitoring campaign was conducted after the second stage of the removal.

The monitoring process determines that a movement of the sediments is observed after each phase of action, depending on the flow rate of that year. The amount of sediment mobilized after the first stages of the removal is higher than the sediments mobilized prior to the removal of the dam.

It can also be concluded that water quality has not been altered after the first stages of the removal.

Habitat and species studies were also conducted because the Inturia dam is an impassable obstacle to the movement of fish. The fish community in the Leitzaran River is: Brown trout (Salmo trutta), Atlantic salmon (Salmo salar), barbel (Luciobarbus graellsii), Adour minnow (Phoxinus bigerri) and eel (Anguilla anguilla). Trout is considered a good indicator in this river.

Within the monitoring process, a 3 km long reach (2 km upstream and 1 km downstream) was monitored by placing 11 sample points in which it was possible to verify the evaluation of the river by taking images at different moments of the year.

Monitoring has been carried out after the fourth stage of the removal as well, but this data is not yet available.

It is considered that the proposal of removal in different stage is adequate and it seems correct to apply this methodology in actions of similar characteristics.

It is also considered adequate to leave a period of time between each stage of the removal so that the sediments can be exported through the river by means of the floods.

Working in stages also avoids impacts on ecosystems. The fish populations of the Leitzaran River have endured well the works.

Lessons learnt

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It is considered that the proposal of removal in different stage is adequate and it seems correct to apply this methodology in actions of similar characteristics.

Image gallery

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Catchment and subcatchment Select a catchment/subcatchment Site Edit site Name WFD water body codes WFD (national) typology WFD water body name Pre-project morphology Reference morphology Desired post project morphology Heavily modified water body No National/international site designation Local/regional site designations Protected species present Yes Invasive species present No Species of interest Atlantic salmon (Salmo salar), Alcedo atthis, Cinclus cinclus, Mustela lutreola, Galemys pyrenaicus, Brown trout (Salmo trutta), Luciobarbus graellsii, Phoxinus bigerri, European eel (Anguilla anguilla) Dominant hydrology Dominant substrate River corridor land use Average bankfull channel width category Average bankfull channel width (m) Average bankfull channel depth category Average bankfull channel depth (m) Mean discharge category 1 - 10 m³/s Mean annual discharge (m3/s) 44 m³/s <br />4,000 l/s <br /> Average channel gradient category Average channel gradient Average unit stream power (W/m2) Project background Edit project background Reach length directly affected (m) Project started 2013/08/01 Works started Works completed Project completed 2016/01/01 Total cost category 100 - 500 k€ Total cost (k€) 242242 k€ <br />242,000 € <br /> Benefit to cost ratio Funding sources The first two stages of the Inturia dam removal were carried out within the scope of the Guratrans project (EFA221/11) while the following two were carried out within the scope of the LIFE Irekibai project (LIFE 14 NAT/ES/00186). Cost for project phases Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname Investigation and design Stakeholder engagement and communication Works and works supervision Post-project management and maintenance Monitoring Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Barriers to fish migration Hydromorphology Continuity for organisms, Continuity of sediment transport, Quantity & dynamics of flow, Flow velocities Biology Fish: Abundance Physico-chemical Temperature, Nutrient concentrations Other reasons for the project It was was an unsafe and unused infrastructure with high maintenance costs. Measures Edit Measures Structural measures Bank/bed modifications Dam removal Floodplain / River corridor Planform / Channel pattern Creation of solid flow regime Other Non-structural measures Management interventions Social measures (incl. engagement) Creation of a path alongside the river, Creation of viewpoint with photos and data of the dam removal Other Monitoring Hydromorphological quality elements Edit Hydromorphological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Biological quality elements Edit biological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Physico-chemical quality elements Edit Physico-chemical quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Any other monitoring, e.g. social, economic Edit Other responses Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Additional links and references Edit links and references Link Description http://europe.wetlands.org/publications/river-fragmentation-analysis-spain/ A link on the Wetlands International website to a document that describes the project. http://www.ecohidraulica.com/ All information on this page is copied from the document mentioned above which is written by Ecohidráulica, S.L. Supplementary Information Edit Supplementary Information References GURATRANS (2014). La demolición de la presa de Inturia: un paso adelante hacia una nueva relación con nuestros ríos. Proyecto EFA221/11 GURATRANS (2014). Seguimiento geomorfológico de los procesos geomorfológicos tras la demolición de una presa en el río Leitzaran. Informe de seguimiento a la demolición de la presa de Inturia tras la segunda fase de derribo. Proyecto EFA221/11 Headwaters Economics (2016). Dam removal: case studies on the Fiscal, Economic, Social and Environmental benefits of dam removal. Ibisate, A., Acín, V., Ballarín, D., Besne, P., Díaz, E., Ferrer-Boix, C., ... & Mesanza, A. Seguimiento geomorfológico del derribo de presas: metodología y primeros resultados (Mendaraz e Inturia, Gipuzkoa). Ibisate, A., Ollero, A., Ballarín, D., Horacio, J., Mora, D., Mesanza, A., ... & Martín-Vide, J. P. (2016). Geomorphic monitoring and response to two dam removals: rivers Urumea and Leitzaran (Basque Country, Spain). Earth Surface Processes and Landforms, 41(15), 2239-2255. Industrial Economics Inc. (2015). Economic & Community Benefits from Stream Barrier Removal Projects in Massachusetts (MA). Massachusetts Department of Fish and Game, Division of Ecological Restoration. LIFE Irekibai project (2015). Resumen de los trabajos de demolición de la presa de Inturia, Fase 3. LIFE Irekibai project (2016). Resumen de los trabajos de demolición de la presa de Inturia, Fase 4. Ojeda, A. O., de Matauco, A. I. G., Naverac, V. A., Ferrer, D. B., Besne, P., Bea, E. D., ... & Martín-Vide, J. P. (2015). Geomorfología y restauración fluvial: seguimiento del derribo de presas en Gipuzkoa. Cuadernos de investigación geográfica, (40), 67-88. Universidad del País Vasco (2014). Cuantificación de la tasa de sedimentos exportados de la cuenca del Río Leitzaran antes, durante y después de la demolición de la presa de Inturia. (IT598/13, Gobierno Vasco)