Changing Coastlines
Question: Identify two natural factors that can shape a coastline.
Answer: Any two of: waves, currents, weather patterns, sea-level change, climate change, tectonic plate movement or sediment movement.
Question: What is fetch, and how does it influence wave formation?
Answer: Fetch is the distance over which wind blows across water. A longer fetch allows more energy to be transferred to the water, generally producing larger waves.
Question: Identify one coastal engineering structure and state its purpose.
Answer: Examples include a groyne, which traps sand; a seawall, which protects land from wave erosion; or a breakwater, which reduces wave energy.
Question: Identify four types of pollution that can affect coastal zones.
Answer: Any four of: organic waste, thermal pollution, toxic compounds, heavy metals, oil, excess nutrients or pesticides.
Question: What is meant by sustainable coastal management?
Answer: Sustainable coastal management protects coastal environments while allowing resources to meet current needs without reducing their availability or condition for future generations.
Question: Define the term sand budget.
Answer: A sand budget is the balance between the amount of sediment entering and leaving a coastal system.
Question: Explain how atmosphere–ocean interactions can produce a sea breeze.
Answer: Land heats faster than the ocean during the day. Warm air rises over the land, and cooler air moves inland from over the ocean to replace it.
Question: What is ecological succession?
Answer: Ecological succession is the gradual process through which organisms colonise an altered or newly available habitat and the biological community changes over time.
Question: Compare point source and non-point source pollution.
Answer: Point source pollution comes from a single identifiable location, such as a discharge pipe. Non-point source pollution comes from widespread or multiple sources, such as agricultural runoff.
Question: Describe one agricultural land-management practice that can improve the health of marine ecosystems.
Answer: Maintaining vegetated buffer zones beside waterways can trap sediment and absorb nutrients before runoff enters rivers and coastal ecosystems.
Question: Compare coastal erosion and accretion.
DOUBLE POINTS
Answer: Erosion occurs when sediment is removed from a coastline, whereas accretion occurs when sediment is deposited and accumulates.
Question: Contrast wave refraction, reflection and diffraction.
Answer: Refraction is the bending of waves in shallow water, reflection is the redirection of waves from a surface, and diffraction is the spreading of waves around an obstacle or through an opening.
Question: Explain how a groyne can cause both accretion and erosion along the same coastline.
DOUBLE POINTS
Answer: A groyne traps sediment on its updrift side, causing accretion. It reduces the sediment supplied to the downdrift side, which can cause erosion.
Question: Describe one abiotic and one biotic method of directly testing water pollution.
Answer: An abiotic test measures a physical or chemical factor such as nitrate, phosphate or heavy-metal concentration. A biotic test measures living organisms, such as faecal coliform bacteria.
Question: Explain how a biotic index can be used to indirectly measure water pollution.
Answer: A biotic index uses the presence, absence or abundance of organisms with different pollution tolerances to estimate the level of pollution and overall water quality.
Question: Explain how tectonic plate movement can change a coastline.
Answer: Tectonic movement can uplift or lower coastal land, create faults and landforms, or generate tsunamis that rapidly erode and reshape coastlines.
Question: Explain how gravitational pull, current strength and wave action influence tidal movement.
Answer: The gravitational pull of the Moon and Sun generates tides. Tidal currents transport the rising and falling water, while waves modify water movement as it reaches the coastline.
Question: Aerial photographs show that a river mouth moved 250 metres north over 20 years. What conclusion can be drawn from this evidence?
Answer: The river mouth and surrounding sediments have gradually migrated north, indicating long-term changes caused by sediment transport, currents, waves or river flow.
Question: Explain how biochemical oxygen demand, or BOD, is used to assess water pollution.
Answer: BOD measures the amount of dissolved oxygen microorganisms use while decomposing organic matter. A high BOD indicates greater organic pollution and less oxygen may remain available for aquatic organisms.
Question: Explain why mussels or seagrasses can be used as marine bio-indicators.
Answer: Their condition, abundance or tissue chemistry changes in response to environmental conditions. Mussels can accumulate pollutants, while declining seagrass health can indicate poor water clarity, excess nutrients or sedimentation.
Question: A beach becomes narrower following several storms and a period of rising sea level. Explain how these factors could have changed the coastline.
Answer: Storm waves removed sediment from the beach, while rising sea level allowed waves to act farther inland. If sediment removal exceeded deposition, the beach developed a negative sand budget and eroded.
Question: Explain how wind, waves and longshore drift could move sand, nutrients and oil along a coastline.
Answer: Wind transfers energy to the ocean and generates waves and surface currents. Waves approaching at an angle produce longshore drift, which transports sand and can also distribute nutrients, oil, debris and other materials along the coast.
Question: Satellite images show decreasing mangrove cover, increasing exposed sediment and expanding urban development over 15 years. Analyse the likely relationship between these changes.
Answer: Urban development may have required mangrove clearing and altered water or sediment flow. The loss of mangrove roots would reduce sediment stabilisation, contributing to increased exposed sediment, erosion and habitat loss.
Question: Explain how fertiliser runoff can cause eutrophication and fish deaths in a coastal lagoon.
DOUBLE POINTS
Answer: Fertiliser adds excess nutrients, causing rapid algal growth. When the algae die, microorganisms decompose them and consume dissolved oxygen. Oxygen levels can then fall low enough to kill fish and other aerobic organisms.
Question: Interpret the water-quality data below.
Site A
Site B
Which site has poorer water quality? Justify your answer using evidence from at least two tests.
Answer: Site B has poorer water quality. It has much higher nitrate and BOD levels, lower dissolved oxygen and fewer pollution-sensitive species. Any two of these results provide evidence of greater pollution.