The impact of water jets that leave the storm drains erodes the sand, damages sea turtle nests and puts one of Mazatlan’s main attractions at risk.
The beach of Olas Altas is losing its sand due to the erosion caused by rainwater discharges that are dumped directly to the center of that coastal ecosystem.
The water bursts generated by the rain last Thursday, August 22, caused the opening of a deep ditch in the beach area. This phenomenon should not be considered as normal, since in reality it is an erosive process that alters the morphology, proportion, and distribution of the sand, warned oceanologist José Antonio Farías Sánchez.
“When the water comes out in the form of jets, it has a very intense erosive effect, in such a way that with the discharge caused by the recent rain, a channel was made in front of it, approximately 10 meters wide, 10 meters long and with an approximate depth of 2 meters, ”he said.
This amounts to a loss of 200 cubic meters of sand, he explained, as these sediments are washed out of the bay when the tide drops (low tide), being exposed to sea currents.
“If we consider the above and the fact that the approximate length of the sandy beach is 200 meters and that the width of the canal is 10 meters, then 20. Rains similar to the aforementioned would be enough to lose almost all of the sand definitely, ”he warned.
The ditch originated by the drain may disappear with the rearrangement of the remaining sand, but that does not mean that the lost sand will be recovered. It is then, only a redistribution of what already exists.
Erosion should be considered a serious problem, said the oceanologist, since the final disappearance of the sand would be reflected in the loss of the sandy beach habitat and its biodiversity, including the sea turtle nesting area and the beach as a space for spreading.
Consequently, there would also be an economic breakdown in the sectors that depend on the seawall and beach of Olas Altas.
On the other hand, the biologist and nature photographer, Alwin van der Heiden, informed that the force of the water that falls through the drainage pipelines is a threat to the conservation of sea turtles, since in recent rains a nest was exposed and their eggs were dragged towards the sea, as shown in the following image provided by the witnesses.
Characteristics of the beach of Olas Altas
The beach of Olas Altas is located in a bay, that is, a concavity in the coastal line. Here a cyclical and unique phenomenon is observed: its sand is loaded towards the north end during summer and towards the south end in winter, according to the direction of the predominant sea current.
This generates a misleading visual perception, as it seems that the large rocks that limit the beach in its upper part move from place, when in reality they are only covered or temporarily discovered by the movement of the sand.
Effect of storm drains
This annual phenomenon has been altered by increasing erosion, which is a consequence of the remodeling of the seawall of this place. With the reconstruction of the street and sidewalks, three rain pipelines have introduced that discharge into the center of the bay.
Defogues occur in the rainy season, just when the sand is in front of the discharge. Before the remodeling of Paseo Olas Altas, the water flowed through the rocky area.
Both José Antonio Farías and Alwin van der Heiden, considered that the problem must be addressed before it worsens and the losses are irreparable.
That same phenomenon was observed in North Beach.
Drainage pipes. Photo: Raquel Zapien
A possible solution to the problem would be to build a cement sink at the base of the storm drain, so that it functions as an area for collecting and distributing water jets, reducing their force and impact on the sand.
The proposal of the interviewees is that this pool be connected to a channel parallel to the wall. Along the channel, pipes were installed to allow water to flow to the beach in the form of small jets and mitigate its erosive effect.
Can you imagine High Waves without a beach?
The Paseo de Olas Altas is located in the oldest section of the Mazatlan boardwalk, between Cerro de la Nevería and Cerro del Vigía.
According to historical records, it initially functioned as a dike to avoid flooding problems in the city, in the 1830s. Subsequently, an embankment was built that was used as urban and recreational space.
Since then, this section of the boardwalk is one of the most representative of Mazatlan and one of the few that still retains its original name.
The Mazatlan Post