What geological hazards lurk in the Khomas region’s soil?
By David Adetona.
Based on an interview with Mako Sitali, Senior Geoscientist at the Geological Survey in the Ministry of Mines and Energy.
The Geological Survey in the Ministry of Mines and Energy has a leading position to ensure and encourage an environment that prevents, reduces or completely avoids geological hazards that have the potential to inflict loss of life and property.
The Survey fulfills its purpose through a systematic process of gathering, collating, assessing and disseminating all information related to disruptions of the earth’s surface that trigger landslides, sinkholes or earthquakes. This is to prevent, prepare, respond or recover from any geological hazard or disaster.
Meanwhile, the National Disaster Plan states: “Without an effective means of communication it will be impossible to implement a well-coordinated emergency operation in Namibia.”
The Khomas region falls in one of the seismic zones which are prone to earthquake due to its geological setting such as the existence of faults within the regional tectonic structures.
The faults are thin cracks in rocks resulting in movement that causes earthquakes. For instance, the Pahl fault around Windhoek is a well-known geological structure that runs north-south from Okahandja to Rehoboth. Smaller faults or rock cracks associated with the Pahl fault are also found in most parts of Windhoek. Faults are relatively common and found in all parts of Namibia.
The bulk of the faults are inactive with only a few that are active, causing small earthquakes. It is therefore essential to emphasise that geological hazards are environmental conditions with short or long-term processes, starting with relatively small fractures but with the potential to cause more serious damage.
The Geological Survey conducted a geotechnical study around Windhoek for future application in land-use planning, civil engineering and general city development.
The pilot project, entitled “Engineering Geological Survey of Windhoek for the Division of Engineering and Environmental Geology” concentrated on mapping and presentation of the most important geological hazards in the city’s territory. The project focused on fault zones and slope processes with related instabilities, as well as mud flows after heavy rainfall, inundation, near-surface ground water, erosion gullies and related issues, for a broad compilation of local geological hazard, vulnerability and risk. It produced a map as a basis for advice on urban land-use and risk-based development planning.
Another phase of the project is planned for this year to complement previous studies for the deployment of a seismic network in the Khomas Region. This will monitor seismicity to identify faults or cracks in the seismically active zones in Windhoek. It will comprise 10 networked seismic stations to monitor earthquakes.
Geological hazard mapping and assessment is an important component of disaster risk management and mitigation to reduce the loss of lives or damage to properties caused by natural disasters.
Awareness of geological hazards reduces the damage caused by earthquakes, floods, droughts and cyclones through an ethic of prevention. Geological hazard mapping explains and identifies various areas that are susceptible or prone to various hazards. Awareness and information dissemination are essential to the public as this may reduce or prevent economic loss or loss of life, property, utilities or infrastructures.
Geological hazard studies reduce the immediate danger by knowing the steps or action to take in the event of a disaster. The level of uncertainty is reduced when individuals and communities are informed about the proper response to and recovery from and emergency situation. Geological hazard awareness is crucial to prevent or be prepared for any future disaster.
Prevent, Prepare, Respond or Mitigate
By combining awareness, education and preparedness, the disruptive impacts of a natural disaster is reduced. For instance, proper zoning and building codes are needed to prevent or reduce actual damage by avoiding certain areas or by enforcing minimum engineering and construction standards.
To be effective, mitigation requires a multidisciplinary approach for prevention, preparedness, response and mitigation. Effectiveness is increased when there is communication and coordination among residents, researchers, practitioners and policymakers.
Locally, the discipline of seismology suffers from a lack of skilled personnel, making it a challenge to anticipate hazardous events, to predict their occurrence, and to respond appropriately.
Furthermore, a dearth of historical data and the condition that all geological hazard responses must be supported by data, make it difficult to give any substantial advice or recommendations.
Additionally, a probabilistic approach to forecast future events, has its limitations as it also depends on historical and incidental data.
Some of the geological hazards can be minimized or prevented by appropriate engineering designs and proactive monitoring. However, the others are beyond human control and unpredictable. Many cities, towns or countries prone to earthquakes now use built-in protection based on building and earthquake codes, or anti-seismic technology designed to protect property and life in buildings.
Such a system can be adopted in the Khomas Region and the rest of the country, implying that any new building or renovation or adjustment of structures must be done according to strict guidelines that would protect or save people from future earthquake, landslides, sinkholes or the collapse of building.