Low-tide elevation - meaning and illustration

1. Characteristics of Low-tide Elevations:

 Key characteristics include:

1. Physical and Geomorphic Characteristics

1. Tidal Exposure

   • Visible only during low tide, LTEs are fully submerged at high tide. Examples include reefs, sandbars, and mudflats.
   • They are surroundedby water at mean lower low water, which is above the level of mean lower low water but not above the level of mean high water;
   • Their elevation relative to sea level determines their exposure duration and ecological function.
2. Composition
   • Formed from natural materials like sediment, coral, or rock. Artificial structures (e.g., seawalls) do not qualify as LTEs under international law.
3. Dynamic Morphology
   • Shape and size can shift due to tidal currents, erosion, or sedimentation, requiring continuous monitoring via satellite imagery (e.g., DEA’s Landsat-based composites).
4. Location: They are situated within a distance of not more than 12 nautical miles from the low-water line of the mainland or of an island;
5. Naturally-formed on the see bed;

2. Legal and Maritime Characteristics

1. UNCLOS Classification

   • Defined under Article 13 of the United Nations Convention on the Law of the Sea (UNCLOS). LTEs lack territorial seas unless located within 12 nautical miles of a coastal state’s mainland or island.
2. Baseline Determinations
   • LTEs can serve as base points for measuring territorial seas if within the 12-nautical-mile threshold. Beyond this range, they hold no legal maritime zones.
   • Straight baselines can only connect LTEs if they host permanent structures (e.g., lighthouses) or have historical recognition.
3. Ownership
   • Automatically belong to the coastal state if situated within its territorial sea, exclusive economic zone (EEZ), or continental shelf.

2. Roles, Biological and Ecological Significance of LTEs

1. Biodiversity Hotspots

   • Intertidal zones on LTEs support unique ecosystems, including mangroves, tidal flats, and coral reefs, which serve as nurseries for marine life.
   • They support various ecosystems, including mangroves, tidal flats, and coral reefs, which serve as nurseries for marine life [3]
2. Coastal Protection
   • Act as natural buffers, protecting coastlines from erosion and storm surges by dissipating wave energy [2].
3. Climate Vulnerability
   • Rising sea levels threaten submerged LTEs, impacting both ecological balance and coastal communities.
4. Intertidal Habitat: LTEs form part of the intertidal zone, the area between high and low tides, creating a dynamic environment that supports unique plant and animal communities [2, 7].
5. Habitat Zonation: The intertidal zone on LTEs is divided into different zones (spray zone, upper, middle, and lower intertidal zones), each with specific conditions and inhabitants [4]. Organisms in higher zones must withstand prolonged exposure to air, temperature extremes, and salinity variations [4].
6. Nutrient and Sediment Exchange: Tides continually move saltwater in and out of these systems, transporting fine sediments and nutrients, which are essential for the ecosystem's productivity [3].
7. Feeding Grounds: The predictable conditions in areas with low tidal ranges allow mobile animals to feed [1].

Further info on signficance of LTE:

• (1) https://wetlandinfo.des.qld.gov.au/wetlands/ecology/components/water-physical/tidal-range/
• (2) https://www.iwr.usace.army.mil/Missions/Coasts/Tales-of-the-Coast/Coastal-Dynamics/Tides/Coastal-Effects-of-Tides/
• (3) https://www.saltmarshguide.org/guide/ecological-setting/
• (4) https://oceanexplorer.noaa.gov/edu/learning/player/lesson10/l10text.htm

3. Low-tide elevations in international law:

Low-tide elevations are addressed in international law, particularly in the United Nations Convention on the Law of the Sea (UNCLOS), with specific implications for maritime boundaries and territorial rights. Pursuant to the 1982 United Nations Convention on the Law of the Sea (UNCLOS), which is the international landmark convention regulating the world's oceans and seas, the following rules are applicable:

• Definition: A low-tide elevation is a naturally formed land area surrounded by water that is above water at low tide but submerged at high tide [1, 3, 4].
• Territorial Sea Claims: According to UNCLOS Article 13, the low-water line on a low-tide elevation can be used as the baseline for measuring maritime zones like the breadth of the territorial sea if the elevation is wholly or partly within the territorial sea from the mainland or an island.
• Restrictions: A low-tide elevation that lies beyond the territorial sea (12 nautical miles) cannot generate its own territorial sea and thus, cannot expand the reach of the territorial sea of a nation.
• Straight Baselines: Straight baselines cannot be drawn to and from low-tide elevations unless lighthouses or similar installations that are permanently above sea level have been built on them, or unless the drawing of straight baselines to and from such elevations has received general international recognition.
• Rights of States: The International Court of Justice has held that low-tide elevations within a state's territorial seas fall under its sovereignty2. States may have certain rights over all low-tide elevations, except for those located on the high seas2. According to the Asia Maritime Transparency Initiative, a low-tide elevation located within the maritime zones of a coastal state automatically belongs to that state (Wikipedia contributors, 2024).
• Artificial Structures: Artificial islands, installations, or structures may be constructed on low-tide elevations5. If constructed within 12 nautical miles of the mainland or an island, that low-tide elevation can be used as a basepoint for measuring the breadth of the territorial sea5.
• Legal title of low-tide elevations: the legal title of low-tide elevations to the territorial sea is derived from the title of the landmass1. They "represent" the landmass and do not have autonomous title to maritime areas1.

4. Low-tide elevation across the globe

1. Technological Monitoring

1. Satellite Mapping

   • Tools like Digital Earth Australia (DEA) use Landsat imagery to create high/low tide composites, visualizing intertidal zones at 25m resolution through its Low Tide Imagery (Landsat).
   • Digital Earth Australia (DEA) offers cloud-free imagery mosaics of Australia's coast, estuaries, and reefs at low and high tide (DEA , 2017). 
   • This product suite visualizes intertidal zones using composite imagery at high and low tide1. 
   • The data, captured at a 25m spatial scale, is generated by calculating the geometric median of the highest and lowest 20% of the observed tidal range from Landsat satellite images.
   • Techniques include tidal height tagging, geomedian composites, and pixel filtering to remove cloud cover.
2. Elevation Modeling
   • Combines tidal data with spatial interpolation to generate 3D elevation maps, aiding habitat conservation and sea-level rise forecasts.
   • 
     
3. Navigation: Tide clocks and global tide APIs are used to navigate tides with precision, benefiting beach lovers, fishermen, surfers, and coastal enthusiasts56.
4. Recreation and Industry: Modern technology might enable the development of LTEs for recreational or industrial facilities2.

4. Tallest Low-tide Elevation in the World

• Bay of Fundy, Canada: This location has the highest tidal ranges in the world, reaching up to 16 meters (52 feet) or even 53.4 feet (134). The unique shape of the bay amplifies the tidal effect (14).

• Ungava Bay, Canada: Tidal ranges here can exceed 15 meters (49 feet) (1).
• Bristol Channel, United Kingdom: The Bristol Channel sees tidal ranges that can surpass 14 meters (46 feet) (1).
• Cook Inlet, Alaska, USA: Cook Inlet experiences tidal ranges up to 12 meters (40 feet) (1).
•  Some sources list the tidal range as 46.9 feet (4).
• Mont-Saint-Michel, France: The tides here can rise up to 14 meters (46 feet) (1).
•  The tidal range can reach up to 44.6 feet (4).

World LTE Sources:

• (1). Coastal Effects of Tides. Institute for Water Resources Website. Retrieved 00:37, February 10, 2025, from https://www.iwr.usace.army.mil/Missions/Coasts/Tales-of-the-Coast/Coastal-Dynamics/Tides/Coastal-Effects-of-Tides/
• (3) https://www.bayoffundy.com/about/highest-tides/
• (4) https://www.whiteclouds.com/top-10/top-10-highest-tides-in-the-world/

Conclusion

Sumary characteristics

• Natural Formation: Low-tide elevations are naturally formed areas of land. 

• The composition doesn't matter as long as it's natural material.
• Tidal Dependence: They are only visible during low tide and disappear when the tide is high [4].
• Maritime Zones: Low-tide elevations can be used as base points for calculating maritime zones, but only if they don't exceed the territorial sea breadth (12 nautical miles) from the mainland or an island [3].
• No Territorial Sea: A low-tide elevation wholly situated beyond the territorial sea's limits does not have its own territorial sea [3, 4]. They don't generate the same rights as islands or other territories [3].
• Baseline Restrictions: Straight baselines cannot be drawn to and from low-tide elevations unless lighthouses or similar installations that are permanently above sea level have been built on them, or unless there is general international recognition for drawing straight baselines to and from such elevations [1].
• Derived Title: The legal title of low-tide elevations to the territorial sea is derived because it proceeds from the title of the landmass [4].

Sumary sources:

• • • (1) https://cil.nus.edu.sg/wp-content/uploads/2012/09/Beckman-LTE-submerged-features-Taipei-20-21-Sep1.pdf
    • (3) https://www.mpil.de/de/pub/publikationen/archiv/world-court-digest.cfm?aktdat=202070000400.cfm&fuseaction_wcd=aktdat
    • (4) https://digitalcommons.pace.edu/cgi/viewcontent.cgi?article=1197&context=pilr

Key Takeaways

• LTEs are transient landforms with legal, environmental, and geophysical significance.
• Their dynamic nature necessitates advanced remote sensing for accurate mapping and policy enforcement.
• Protection of LTEs is critical for preserving coastal biodiversity and mitigating climate impacts.

By integrating legal frameworks like UNCLOS with technologies such as Landsat imagery, stakeholders can better manage these vital yet vulnerable features.

Sources:

1. Hugo Ignacio Llanos (2002). Low-Tide Elevations: Reassessing Their Impact on Maritime Delimination. 14 Pace Int'l L. Rev. 255 (2002) Retrived from https://digitalcommons.pace.edu/cgi/viewcontent.cgi?article=1197&context=pilr
2. Wikipedia contributors. (2024, September 6). Low-tide elevation. In Wikipedia, The Free Encyclopedia. Retrieved 00:37, February 10, 2025, from https://en.wikipedia.org/w/index.php?title=Low-tide_elevation&oldid=1244302926
3. DEA . (2017). DEA High and Low Tide Imagery (Landsat). Retrieved 04:37, February 10, 2025, from https://en.wikipedia.org/w/index.php?title=Low-tide_elevation&oldid=1244302926
4. Sagar, S., Phillips, C., Bala, B., Roberts, D., Lymburner, L., 2018. Generating continental scale pixel-based surface reflectance composites in coastal regions with the use of a multi-resolution tidal model. Remote Sensing. 10, 480. https://doi.org/10.3390/rs10030480 [Accessed 10 February 2025]