Why is coastline important

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Notify me of new posts via email. Share this: Twitter Facebook. Like this: Like Loading Leave a Reply Cancel reply Enter your comment here Fill in your details below or click an icon to log in:. Email required Address never made public. Coasts are important for many different reasons and for different groups of people. They provide:. You can probably think of many more reasons why coasts need to be protected. Figure 2. The highest waves occur in the Southern Ocean and north Pacific and Atlantic where they are generated by strong sub-polar lows.

Tides and tidal currents. Figure 3. Tidal inlet at Merrimbula, Australia. Wind and currents. Winds blowing over the oceans are responsible for generating ocean waves. Nearer the coast they can generate local seas — they can move the ocean surface and generate locally wind driven currents which in places can result in upwelling and downwelling. Finally, when blowing over the beach, they can transport sand inland to build coastal sand dunes.

Fluvial-deltaic systems. Figure 4. The Gasgoyne River delta in Western Australia delivers large volumes of sand to the coast where it is deposited in river mouth shoals and slowly reworked longshore to supply downdrift spits, barriers, and dunes.

Sea level. Sea level determines the position of the shoreline. During the last glacial maxima ice age 18, years ago, sea level was m below present, and the continental shelves were exposed. It then rose, reaching present sea level around 6, years ago, after which it was relatively stable. Now, with climate change, it is beginning to rise again, and may rise as much as 1 m over the next years, triggering shoreline retreat, inundation, and erosion.

Beach Systems. What is a beach? Figure 5. An idealised cross-section of a wave-dominated beach system consisting of the swash zone which contains the subaerial or 'dry' beach runnel, berm, and beach face and is dominated by swash processes; the energetic surf zone bars and channels with its breaking waves and surf zone currents; and the nearshore zone extending out to wave base where waves shoal building a concave upward slope.

Figure 6. Figure 7. Beach sub-systems. Figure 8. View of Makapu Beach, Hawaii, showing waves shoaling and steepening as they travel across and interact with the nearshore zone, then breaking across the surf zone.

Figure 9. Figure Wave runup on the steep beach face at Ke lli Beach, Hawaii. A steep reflective beach with well developed high tide beach cusps at Hammer Head, Western Australia.

Beach types. Beaches can range from low energy systems, where small waves lap against the shore, to those with high waves breaking across several hundred meters of surf zone. They can also be exposed to micro 8 m. A plot of breaker wave height versus sand size, together with wave period, that can be used to determine the approximate beach state for wave-dominated beaches. Well-developed intermediate beach containing transverse bars and rip channels along Lighthouse Beach, Australia.

A steep reflective high tide beach face fronted by a m wide tide-modified low tide terrace crossed by shallow drainage channels at North Harbour Beach, Australia.

A narrow high tide beach fronted by 1 km wide inter-tidal sand flats, upper Spencer Gulf, South Australia. The beach at Pingok Island, north Alaska, shown a during summer, with floating ice against the shore; b during freeze-up, with snow and sea ice accumulating; and c the frozen winter beach and ocean.

Beaches and barriers. A coastal sand barrier consisting of a beach and vegetated dunes, backed by a lagoon, at Big Beach, Queensland, Australia. A series of low barrier islands separated by tidal inlets, at Corner Inlet, Victoria, Australia. Share Cancel. Revoke Cancel. Keywords Keywords for this Article. Save Cancel. Flag Inappropriate The Content is: Objectionable. Flag Content Cancel. Email your Friend. Submit Cancel.

This content is currently under construction. Explore This Subject. Key Challenges. Earth's Climate System. Biogeography: Distribution, Dispersal, and Diversification of Organisms. Coastal changes can take hundreds of years. The way coasts are formed depends a lot on what kind of material is in the land and water. The harder the material in the land, the harder it is to erode.

Coastlines of granite , a hard rock, stay pretty stable for centuries. Sugarloaf Mountain, on the coast of Rio de Janeiro, Brazil, is made mostly of granite and quartz. It has been a landmark for centuries. The famous White Cliffs of Dover, in England, are made of calcium carbonate.

This is a soft material and erodes easily. However, it exists in such great quantities that years of erosion have not made a visible impact on the coastline. The other coast is French.

The sandy coastlines of islands, on the other hand, change almost daily. The island of Mont Saint Michel is only an island when the tide is in. It is part of the coast of France during low tide. Islands are also the site of Earth's newest coastlines, like a Tongan island created in March by the eruption of the volcano Hunga Tonga-Hunga Haapai. The "Big Island" of Hawaii, created by five volcanoes, sometimes expands its coastline when one of its active volcanoes, Mauna Loa or Kilauea, erupts.

If lava flows reach the ocean, the lava cools and forms new coastline along the Pacific Ocean. Tides, the rise and fall of the ocean, affect where sediment and other objects are deposited on the coast.

The water slowly rises up over the shore and then slowly falls back again, leaving material behind. In places with a large tidal range the area between high tide and low tide, waves deposit material such as shells and hermit crabs farther inland. Areas with a low tidal range have smaller waves that leave material closer to shore. Waves that are really big carry a lot of energy.

The larger the wave , the more energy it has, and the more sediment, or particles of rock, it will move. Coastlines with big beaches have more room for waves to spread their energy and deposits. Coastlines with small, narrow beaches have less room for waves to spread out. All the waves' energy is focused in a small place. This gives the small beaches a tattered, weathered look.