Model Answer
0 min readIntroduction
Coastal regions are vulnerable to various marine hazards, among which storm surges and seiches pose significant threats. While both involve abnormal rises in water level, their origins and characteristics differ considerably. A storm surge is a response to meteorological forces, typically associated with tropical cyclones, while a seiche is a standing wave generated by disturbances within enclosed or semi-enclosed bodies of water. Understanding these differences is crucial for effective coastal management and disaster preparedness.
Storm Surges
Storm surges are abnormal rises in sea level during a storm, primarily caused by strong winds pushing water towards the shore. The low atmospheric pressure within the storm also contributes to the rise. These surges are most common during tropical cyclones (hurricanes, typhoons) and intense extratropical storms.
- Scale: Large-scale, affecting extensive coastlines (hundreds of kilometers).
- Trigger: Meteorological – strong winds and low pressure systems.
- Water Movement: Primarily horizontal movement of water towards the coast.
- Duration: Relatively short-lived, coinciding with the storm’s passage (hours to days).
- Impacts: Widespread flooding, erosion, infrastructure damage, loss of life.
The Bay of Bengal and the coast of Bangladesh are particularly vulnerable to storm surges due to the shallow continental shelf and funnel-shaped coastline.
Seiches
Seiches are standing waves in enclosed or semi-enclosed bodies of water, such as lakes, bays, and harbors. They are caused by disturbances that displace the water, like strong winds, atmospheric pressure changes, or even seismic activity. Unlike storm surges, seiches are not directly linked to storms.
- Scale: Localized, affecting specific bodies of water (kilometers).
- Trigger: Non-meteorological – wind setup, atmospheric pressure fluctuations, seismic activity, or even passing ships.
- Water Movement: Oscillatory – water sloshes back and forth within the basin.
- Duration: Can persist for hours or even days after the initial disturbance.
- Impacts: Fluctuating water levels, disruption of navigation, damage to waterfront structures.
Lake Michigan in the USA is known for experiencing significant seiches, particularly during strong wind events.
Comparative Analysis
| Feature | Storm Surge | Seiche |
|---|---|---|
| Cause | Strong winds & low pressure of storms | Disturbances in enclosed/semi-enclosed water bodies |
| Scale | Large (hundreds of km) | Localized (kilometers) |
| Trigger | Meteorological | Non-meteorological |
| Water Movement | Horizontal inflow | Oscillatory (sloshing) |
| Duration | Hours to days | Hours to days (can persist) |
Conclusion
In essence, storm surges are large-scale, storm-driven events impacting extensive coastlines, while seiches are localized, oscillatory waves within confined water bodies. While both can cause coastal hazards, their underlying mechanisms and spatial scales differ significantly. Effective coastal management requires understanding these distinctions to implement appropriate mitigation strategies and early warning systems. Further research into predicting both phenomena is crucial given the increasing frequency of extreme weather events and seismic activity.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.