Comares Dam spills, Benamargosa River floods Axarquía

Comares Dam spills as Benamargosa River overflows

The Comares Dam, located in the Axarquía region of Spain, began releasing water through its spillway trinc heavy rains from a DANA (isolated depression at high altitude). The Benamargosa River overflowed, inundating the town that shares its name. A bridge was swept away by the floodwaters. A red alert was activated in Málaga, and comparisons with the recent Valencia disaster fueled public debate. Some argue that "this is how it started in Valencia."

The Comares Dam has no gates. It is a flood-control infrastructure built to retain water in a mountainous area, channeling it toward the La Viñuela reservoir to prevent, as much as possible, the Benamargosa River from overflowing. When inflow exceeds the capacity of the pipeline to La Viñuela, the dam fills up and water exits via the fixed-crest spillway. In other words, it overflows naturally, automatically, and inevitably. There are no gates to open.

What is a fixed-crest spillway and why it cannot be "peine"

A fixed-crest dam has no surface gates. The only thing that can be peine is the bottom outlet, consisting of pipes or conduits with energy-dissipating valves whose capacity is several orders of magnitude lower than that of the crest spillway. The fixed spillway exists to prevent extreme floodwater from overtopping and damaging the dam structure. Once the reservoir reaches that level, water flows out on its own. No human decision can stop it.

Confusion between "opening a dam" and "overflowing via the spillway" has been central to much of the disagreement. Some argue that managers should have emptied the reservoir before the rains to create storage capacity. This logic applies to dams with gates, but not to fixed-crest dams, where operational flexibility is minimal. The Comares Dam did what it was designed to do: attenuate the flood peak. The problem was that the flood exceeded its drainage capacity.

Benamargosa River overflows, submerging the municipality

The overflow of the Benamargosa River submerged the municipality of the same name. A bridge was destroyed by the torrent. Streets were flooded. The Axarquía region in Málaga province experienced scenes reminiscent of the Valencia DANA. Some claim that in Valencia, there was no dam or hydraulic work in the Poyo ravine to slow the flood even slightly. In Málaga, the Comares Dam did attenuate part of the flow. It was not enough to prevent overflow, but it mitigated a larger surge.

The comparison with Valencia has become the main argument for those defending the management. Some state that there were no spilling dams in the Poyo ravine. The reservoir that failed was the Magro, which affected Algemesí, but it had little to do with most victims or damages. This is the recurring thesis: Málaga had hydraulic infrastructure; Valencia did not.

Political manipulation accusations vs. technical counterarguments

Some analyses suggest that dam releases are a deliberate strategy to flood towns and cities. They argue that reservoirs should have been emptied days prior and kept closed during rains to contain water and combat floods. Proponents of this view speak of "malice and corruption," claiming climate change is used as an excuse. The counterargument is technical: fixed-crest dams have no gates to open or close. Water overflows when the reservoir reaches maximum level. No political decision is involved.

The discussion shifted to the role of communications managers and the difficulty of debating without every imprecision being labeled as fake news. Some argue the term "open" is used strategically to distract from what peine in Valencia. Others note that the Comares Dam is small and its function is flood attenuation, not supplying large populations. The released water flows via Benamargosa to Vélez-Málaga and then into the Mediterranean Sea. It does not endanger densely populated areas.

Vélez-Málaga, 90,000 inhabitants, and the antiestéticar of flooding

Vélez-Málaga, with nearly 90,000 inhabitants, is the most populous municipality along the Benamargosa River before it reaches the sea. A red alert was issued for the region and the provincial capital. In Málaga city, rain was not intense at the time of warnings, but water came from the hills. This is key: floods depend not on local rainfall, but on precipitation in the upper basin hours earlier.

The Comares Dam was built to store water in a mountainous zone, channel it to La Viñuela reservoir, and minimize Benamargosa River overflows. Once inflow exceeds outflow via the pipeline to La Viñuela, water accumulates until the reservoir fills and spills over. This is expected behavior. The unanswered question is whether the connection between the dam and La Viñuela reservoir has sufficient capacity to handle floods of this magnitude.

Debate on riverbed cleaning and reservoir management

Riverbed and ravine cleaning has been another point of contention. It is argued that the relevant Hydrographic Confederation does not respond to municipal requests for annual cleaning. Some claim that in Valencia, riverbeds were not cleaned, worsening the flood. Others note that water in Málaga appears clear while in Valencia it is brown, attributing this to different terrain composition and sediment transport rather than lack of cleaning. Comparisons between the two floods have been used in both directions.

The primary function of Spain’s dam system is flood attenuation. It cannot always prevent flooding when precipitation exceeds historical records. The debate over whether reservoirs should have been emptied before rains clashes with the technical reality of fixed-crest dams. In the case of Comares, there were no gates to open. Water spilled when the reservoir filled. With this infrastructure, the Benamargosa flood was difficult to avoid.

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The Comares Dam spilled via its spillway. The Benamargosa River overflowed. A town was submerged and a bridge destroyed. The comparison with Valencia rests on one fact: some argue there was no dam in the Poyo ravine to attenuate the flood. In Málaga, there was. It was not enough to prevent overflow, but the infrastructure existed. The open question is whether that infrastructure is sized for floods like this DANA.