Expansion of land subsidence in coastal areas

According to RCO News Agency, Dr. Abolqasem Gourabi, a member of the faculty of Tehran University, in the webinar “Land Subsidence” emphasized the necessity of holding extensive meetings about this phenomenon and said: When I briefly look at the subsidence situation in Iran, I really don’t know which sector or which group of people are not affected by it; But the alarm of land subsidence has been sounded since about 15 years ago, and today its signs are observed in different parts of the country with significant intensity.

Stating that subsidence in the country is a major environmental challenge, he said: the academic environment deals mostly with theoretical issues, but these issues should move towards problem solving and providing solutions for the country’s problems.

Gourabi added: In order to hold this webinar, we tried to have a meeting different from previous meetings; For this purpose, a Telegram group was created to collect and categorize the questions based on the sent questions. The topics discussed in this meeting include four sections: definitions, concepts, reasons, drivers, effects and consequences, and challenges, as well as monitoring techniques.

The member of the academic staff of Tehran University considered the second part of this meeting to be devoted to the issue of investigating the subsidence situation in Iran and reminded: But the reality is that the subsidence situation in Iran is not suitable. The third part of the meeting is related to subsidence management; An issue that Iranian society needs now more than ever, and with the presence of experts present, we can hope that effective solutions will be proposed.

Gourabi considered the subsidence of the earth to be a gradual subsidence or a vertical downward movement of the earth’s surface and continued: aquifers are like sponges; If water is removed excessively from them, due to the reduction of pore water pressure, the upper layers are compressed and subsidence occurs.

Referring to the factors that trigger subsidence and the complexity of the trigger mechanisms of this phenomenon, the faculty member of Tehran University said: The question that arises is which factors are really the triggers of subsidence and why has the process of subsidence accelerated so much in the last seven to eight years? In this context, we need to identify the trigger mechanism to understand why wherever there is talk of subsidence in the country, somehow everyone is involved in this problem.

Gourabi referred to the subsidence phenomenon as a multi-system civilization super-crisis and reminded: this phenomenon has now found multiple dimensions and involved multiple systems; From national security to infrastructure and various economic and social fields.

Referring to the research conducted in universities in the field of subsidence detection, he pointed out: in this field, universities have acted very strongly; Numerous theses have been compiled in different faculties about subsidence, and especially with the introduction of remote sensing techniques, the monitoring has changed from descriptive mode to millimeter measurement. Today, many field tools and methods are available; Various gauges and even drones have provided the possibility of accurate monitoring. For example, our faculty has a drone that, if we obtain a flight permit, we can use it to identify the condition of the zones and verify the presence of subsidence in the field.

Gourabi said about the state of subsidence in Iran and the world: the researches show that the coastal areas of the world are not safe from the phenomenon of subsidence, and practically, you can find very few watersheds that do not have problems.

The faculty member of Tehran University also addressed the question raised by some audience members about the role of earthquakes in subsidence and said: One of the very correct technical questions is why we always consider the excessive withdrawal of underground water to be the first culprit of subsidence? If we affect an aquifer and make changes in its level, won’t those changes themselves cause subsidence? This is a technical question and should be investigated with accurate data and models.

He added that relatively small earthquakes or the occurrence of seismic events may also play a role in intensifying subsidence, and this issue requires accurate temporal and spatial analysis.

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