# Chapter 11 Study Guide Answers: Coastal Hazards

This companion document answers the questions in `NaturalHazards.Chapter11.StudyGuide.v2.md`. Answers are organized to match the study guide: section review questions first, then the chapter-wide comparison questions and the practice questions. Wording and figures were checked against the textbook chapter `NaturalHazards.Chapter11.md`.

## Answers to Section Review Questions

### 11.1 Introduction to Coastal Hazards

1. **How does plate tectonics influence coastlines?** Plate tectonics determines whether a coast is **tectonically passive** or **active**. Passive coasts (east coasts of the U.S. and Canada, the Canadian Arctic) are far from plate boundaries and typically have wide continental shelves with barrier islands and sandy beaches; rocky shorelines are mostly limited to New England, Atlantic Canada, and Arctic islands. Active coasts (west coasts of the U.S. and Canada near the San Andreas and Cascadia boundaries, plus Hawaii, Puerto Rico, the Virgin Islands, and southern Alaska) experience mountain building that produces sea cliffs and rocky shorelines, with fewer long sandy beaches. Climate and organisms also modify coasts.

2. **What are the most serious coastal hazards?** (1) Strong coastal currents, including rip currents in the surf zone and tidal currents in narrow bays and channels; (2) coastal erosion of beaches, dunes, and sea cliffs; (3) storm surge from tropical and extratropical cyclones; and (4) tsunamis, especially along the Pacific Ocean.

### 11.2 Coastal Processes

1. **What three factors determine the size of waves?** The **velocity (speed) of the wind**, the **duration** of the wind, and the **fetch** (the distance the wind blows across the water surface).

2. **What are rogue waves?** Rogue waves are unusually large waves that are much bigger than surrounding waves. They form mainly by **constructive interference** when multiple similarly sized waves intersect with their crests and troughs matching, and are also influenced by undersea irregularities and currents. They are dangerous to ships and beachgoers.

3. **Define wave height, wavelength, wave period, and wave energy.** **Wave height (H)** is the difference in height between the trough and crest. **Wavelength (L)** is the distance between successive crests. **Wave period (T)** is the time in seconds for successive waves to pass a reference point. **Wave energy** is approximately proportional to the square of wave height.

4. **What is wave refraction?** Wave refraction is the bending of a long wave front as it slows in shallow water. It causes wave energy to **converge on headlands** (producing larger waves and more erosion) and to **diverge along adjacent shorelines** (lower energy), so erosion tends to straighten the coastline.

5. **Define plunging and spilling breakers.** **Plunging breakers** peak quickly and plunge or curl; they form on steep beaches and are more erosive. **Spilling breakers** gently spill; they form on wide, nearly flat beaches and are more likely to deposit sand.

6. **What defines a beach?** A beach is a landform consisting of loose material (such as sand or gravel) that has accumulated by wave action at the shoreline. Its color and composition reflect the source of the material.

7. **What is littoral transport?** Littoral transport ("littoral" means shore) is the movement of sediment parallel to the shoreline in the swash and surf zones. It includes beach drift and longshore drift.

8. **Differentiate between beach drift and longshore drift.** **Beach drift** is the zigzag movement of sediment in the swash zone caused by the up-and-back motion of waves. **Longshore drift** is the transport of sediment by **longshore currents** that flow essentially parallel to the shoreline in the surf zone. Together they form littoral transport; both occur when waves strike the coast at an angle.

### 11.3 Sea-Level Change

1. **Define relative and eustatic sea-level rise, and explain the corresponding coastal hazards.** **Relative sea level** is the sea level observed at a particular coast; it reflects both land movement and water movement. **Eustatic sea level** is global sea level, controlled by the volume of water in the oceans and the shape of ocean basins. Rising sea level (from thermal expansion and melting ice) increases hazards from storm surge, coastal erosion, and flooding; low-lying, gently sloping, and subsiding coasts are most threatened, and low Pacific atolls may be inundated.

2. **How does sea level change temporarily for very short periods of hours or days?** Mainly through weather: **wind speed** (which has a greater effect than atmospheric pressure) and changes in **atmospheric pressure** raise or lower the water, with **storm surge** as an extreme case. **Astronomical tides** cause regular daily and seasonal changes, and **El Niño** can change sea level by up to about 30 cm (12 in.) over days to months.

### 11.4 Geographic Regions at Risk from Coastal Hazards

1. **List factors that help determine the rate of coastal erosion at a particular beach.** The resistance of the earth materials, the energy of the waves (surf conditions and storms), sand supply (the beach budget), the presence of protective dunes or sea cliffs, coastline orientation and exposure, subsidence and relative sea-level rise, and human structures and activities.

2. **Why are average rates of erosion at the regional scale useful but difficult to interpret?** Regional averages are useful for broad planning and comparison, but local conditions — rock type, the amount of sand on a beach, the presence of a seawall or groin, and the timing of storms — vary so much that an average rate may not describe any specific site. Local conditions and specific events can cause erosion much faster or slower than the regional average.

### 11.5 Effects of Coastal Processes

1. **How are rip currents produced, and how can you escape from one?** Rip currents form when a series of large waves piles up water between the longshore bar and the swash zone; the water does not return the way it came but escapes offshore through narrow gaps in the longshore bar, forming fast currents that can exceed 6 km/hr. To escape, **do not panic** and do not try to swim straight back; swim **parallel to the shore** until outside the current, then swim to shore, and if you cannot, wave and yell for help.

2. **Why is the beach budget such a valuable tool in risk analysis for coastal erosion?** The beach budget accounts for the input, storage, and output of sand, showing whether a beach is growing or eroding and why (for example, when a dam reduces river sediment supply). It helps predict future shoreline change and evaluate the likely effects of management options before they are applied.

3. **Assume there are several beach homes near point X in our beach budget example. What advice would you give them based on the calculations? What would be your response if there were high-rise coastal resorts near point X?** After the dam was built, the budget at point X became **-5,500 m³/yr**, meaning output exceeds input and the beach is eroding. For **beach homes**, I would advise expecting continued shoreline retreat, avoiding hard structures that worsen erosion, considering managed retreat/relocation, and supporting restoration of sediment supply or beach nourishment. For **high-rise resorts**, relocation is impractical, so protection options (beach nourishment, groins with renourishment, or structures) could be considered, but with the understanding that they are expensive, require maintenance, and may harm adjacent beaches.

### 11.6 Linkages between Coastal Processes and Other Natural Hazards

1. **How are coastal processes linked to other hazards, such as earthquakes, tsunamis, landslides, volcanic eruptions, hurricanes, and flooding?** Earthquakes, volcanic eruptions, and tsunamis can radically reshape shorelines. Cyclones produce storm waves, storm surge, and coastal flooding that drive erosion, and storm surge plus heavy inland rain causes widespread flooding. Subsidence makes coasts more vulnerable to both freshwater flooding and storm surge. Wave erosion undercuts sea cliffs and bluffs, triggering landslides (worsened when structures add weight at the top). El Niño can increase West Coast extratropical cyclones and erosion (as in 1982-83), and climate change and sea-level rise increase the energy of storms and the reach of erosion and flooding.

### 11.7 Natural Service Functions of Coastal Processes

1. **List some of the natural service functions of beaches.** Beaches transport and store sand; supply sediment to lagoons, estuaries, and dunes; dissipate wave energy as a buffer; break down pollutants and cycle nutrients; provide nesting and roosting habitat for shorebirds and seabirds; filter and discharge groundwater; maintain biodiversity (such as California grunion); provide food sources for shorebirds and fish; and offer cultural, aesthetic, and recreational value. Coastal erosion also creates scenic features (cliffs, headlands, sea arches) and is often the only significant source of beach sand.

### 11.8 Human Interaction with Coastal Processes

1. **Describe the main causes of erosion at Assateague Island, located just south of Ocean City on Fenwick Island.** The **jetties built in 1935** to stabilize the Ocean City inlet block the natural southward longshore drift of sand. This starves the north end of Assateague Island of sand, causing shoreline erosion of about **11 m per year** (nearly 20 times the long-term rate for the Maryland coast), while beaches immediately north of the inlet widened.

2. **What factors affect the severity of erosion on Great Lake shorelines? How applicable are these factors to general coastal erosion?** Factors include **lake level** (high levels cause the most erosion), **coastal dunes** (dune-protected bluffs erode more slowly), **coastline orientation** (sites exposed to high-energy storm winds erode faster), **groundwater seepage** (seepage at the bluff base causes instability and erosion), and **protective structures** (locally beneficial but often accelerate adjacent erosion). These factors apply generally to coastal erosion elsewhere, since water level, protective dunes, exposure, groundwater, and structures affect erosion on all coasts.

### 11.9 Minimizing the Effects of Coastal Hazards

1. **How can a seawall increase beach erosion?** A seawall's vertical face reflects incoming storm waves and redirects their energy to the shore. Over decades this promotes beach erosion and produces a narrower beach with less sand, and the wall can fail by being overtopped or undermined.

2. **Why are beach groins used? What problems can groins cause?** Groins are built perpendicular to the shore to trap a portion of the sand moving in longshore drift, widening the beach **updrift**. The problem is that they cause erosion **downdrift**, because the longshore drift is depleted of sand; a groin or groin field thus protects one stretch of beach at the expense of the adjacent shoreline. Nourishing the groin with added sand can reduce downdrift erosion.

3. **Why do breakwaters and jetties cause beach erosion problems?** Both block littoral transport. **Breakwaters** trap sand and alter the coastline, causing deposition and erosion and sometimes blocking harbor entrances with trapped sand, requiring artificial sand bypassing. **Jetties** keep channels open but cause the updrift beach to widen while contributing to erosion of downdrift beaches. It is impossible to build a breakwater or jetty that does not interfere with longshore sand movement.

4. **What are the advantages and disadvantages of beach nourishment?** **Advantages:** it imitates natural processes (a "soft solution"), is aesthetically preferable to structures, provides a recreational beach, and gives some protection from erosion and storms. **Disadvantages:** it is expensive, must be repeated at regular intervals, requires a suitable range of sand sizes and a nearby source, and a single large storm can remove much of the added sand (it is "sacrificial").

5. **What is coastal zone bioengineering, and what are its advantages and possible shortcomings?** Coastal zone bioengineering uses living or dead plants to assist erosion control — for example, dunes stabilized with native dune grasses, the use of Sargassum seaweed in Galveston, Texas, and the dense palm root systems near the high-tide line at Refugio State Beach, California. **Advantages:** environmentally compatible, comparatively low cost, and aesthetically pleasing. **Shortcomings:** it is a relatively new concept still being tested and provides only a weak first defense that may not withstand major storms or high tides.

### 11.10 Perception of and Adjustment to Coastal Hazards

1. **What are the main adjustments to managing coastal erosion?** They fall into three categories: (1) **beach nourishment** ("soft" solution imitating natural processes); (2) **land-use change**, avoiding hazardous areas or relocating threatened buildings — the "managed retreat" solution (also soft); and (3) **shoreline stabilization** with structures such as groins and seawalls ("hard" solution). For strong currents, education, awareness, supervised swimming, and posted warnings are the main adjustments.

2. **What are the attributes of adaptive management?** It is a structured management concept that (a) uses science, statistical analysis, and modeling to reduce management uncertainty; (b) promotes sustainable coasts and beaches for future generations; (c) communicates alternatives for discussion and negotiation (an open process); and (d) recognizes that future change is inevitable and that management can change as conditions change.

3. **What are the goals of integrated coastal zone management?** To maintain the ecological function and integrity of the coastal zone; to encourage sustainable solutions to coastal zone management; and to reduce or minimize present and potential conflicts resulting from development, resource use, and recreational use of the coastal zone.

4. **What are E-lines and E-zones?** **E-lines** mark the expected position of erosion after a given number of years (for example, the E-10 line is the shoreline's expected location in 10 years). **E-zones** are the areas between the shoreline and the E-lines, similar to floodplain hazard zones. They establish setback distances: rising sea level is treated as an imminent hazard in the E-10 zone, movable structures are allowed in the intermediate and long-term zones (E-10 to E-60), and permanent large structures are allowed only landward of the E-60 line. New structures seaward of the E-60 line should be built on pilings designed to withstand a 100-year storm.

5. **Why was moving the Cape Hatteras Lighthouse successful?** It was a successful **managed retreat** solution. The 4,400-ton lighthouse had been about 500 m from the ocean when built but only about 100 m away by the early 1990s. In 1999 it was moved more than 800 m inland using 120 hydraulic jacks in a "Unified Jack System," after "proof rolling" the route to test for subsurface holes. At its new location it should be safe for 50 to 100 years, rather than being destroyed by erosion at its old site.

6. **Could erosion control measures for Pointe du Hoc in France be widely applied to other eroding sea cliffs? Why or why not?** No. The Pointe du Hoc approach — filling sea caves at the cliff base with several hundred cubic meters of concrete and using rock bolts, at a cost of about $6 million — is a **site-specific, temporary hard solution** for a short length of cliff. The project was justified by the site's historical importance, and the study estimated it would reduce retreat by only about half (the upper weak soil still produces small landslides). Applying such measures to a long section of sea cliff would be far too expensive to maintain, and new sea caves could form, so managed retreat (moving structures inland) is generally preferable in the long run.

## Answers to Chapter-Wide Comparison Questions

1. **How do tectonically passive and active coasts differ in landforms and coastal processes?** Passive coasts are far from plate boundaries and typically have wide continental shelves, barrier islands, and sandy beaches (rocky shores only locally). Active coasts are near plate boundaries, where mountain building yields sea cliffs and rocky shorelines, with fewer long sandy beaches; they also experience tectonic uplift and earthquakes.

2. **How do wave height, wavelength, wave period, and wave energy relate?** Wave height is the trough-to-crest difference; wavelength is the crest-to-crest distance; wave period is the time for successive waves to pass a point. Wave energy is approximately proportional to the square of wave height, so doubling wave height quadruples energy.

3. **How do spilling and plunging breakers differ, and what does each do to a beach?** Spilling breakers spill gently on wide, flat beaches and tend to deposit sand (building beaches); plunging breakers peak and curl on steep beaches, are more erosive, and cause much of the coastal erosion during storms.

4. **How does wave refraction concentrate or disperse energy along a shoreline?** As wave fronts bend in shallow water, wave energy converges on protruding headlands (higher waves, more erosion) and diverges along adjacent shorelines (lower energy, deposition), which tends to straighten the shoreline over time.

5. **How do beach drift and longshore drift combine in littoral transport?** Beach drift moves sediment in a zigzag path in the swash zone; longshore drift moves sediment with longshore currents in the surf zone. Together they constitute littoral transport, moving sand parallel to shore, and both operate when waves strike the coast at an angle.

6. **How do eustatic and relative sea level differ, and what processes control each?** Eustatic sea level is global, controlled by the volume of ocean water (thermal expansion and melting ice) and the shape of ocean basins (plate tectonics). Relative sea level is what is observed at a coast and reflects both water movement and land movement (tectonics, isostatic rebound, subsidence, deposition/erosion), plus short-term tides and weather.

7. **How do rising sea level, subsidence, and tides affect coastal flooding and erosion?** Rising sea level and subsidence lower the land relative to the sea, increasing the reach and frequency of storm surge, flooding, and erosion; tides add to surge when landfall occurs at high tide, and tidal currents can be hazardous in narrow bays and channels.

8. **Why do coastal erosion rates vary along the Atlantic, Gulf, Pacific, and Great Lakes coasts?** Because of differences in rock and sediment resistance, wave energy and storm exposure, sand supply, subsidence, protective features, and human modification. Southeastern barrier islands average 0.3-1.0 m/yr (up to 8 m/yr locally); Florida/Gulf 0.3-2 m/yr; Great Lakes average 0.3-1 m/yr (up to 15 m/yr); and the West Coast 0.1-0.3 m/yr.

9. **How do rip currents form, and how does the beach budget help evaluate erosion?** Rip currents form when piled-up water returns offshore through gaps in the longshore bar, creating fast narrow currents. The beach budget quantifies sand inputs, storage, and outputs to show whether a beach is growing or eroding and why, which is essential for predicting change and choosing management options.

10. **How do sea cliffs and lakeshore bluffs erode, and how can people increase the rate?** They erode through the combined action of waves (especially plunging breakers during storms) and land processes (running water and landslides). People can accelerate erosion by increasing surface runoff and groundwater discharge (watering lawns, poor drainage) and by adding weight from structures, walls, and pools on top of the cliff.

11. **How are coastal processes linked to earthquakes, tsunamis, cyclones, flooding, landslides, and subsidence?** Earthquakes, volcanic eruptions, and tsunamis reshape shorelines; cyclones cause storm surge, waves, and coastal flooding; subsidence increases flood and surge vulnerability; wave erosion undercuts cliffs and causes landslides; and climate change/sea-level rise increase storm energy and the reach of erosion and flooding.

12. **What natural service functions do beaches and coastal processes provide?** They transport and store sand, supply sediment to lagoons/estuaries/dunes, dissipate wave energy, break down pollutants, cycle nutrients, provide wildlife habitat, filter groundwater, maintain biodiversity, provide food, create scenic/aesthetic features, and offer recreation.

13. **How do barrier-island development, dune removal, and engineering structures alter coastal processes?** Development increases exposure; dune removal eliminates natural surge protection; and structures (jetties, groins, seawalls, breakwaters) interrupt littoral transport, causing updrift deposition and downdrift erosion (for example, the Ocean City jetties starved Assateague Island).

14. **How do seawalls, groins, breakwaters, and jetties affect erosion and deposition?** Seawalls reflect wave energy and promote beach erosion; groins trap sand updrift and erode downdrift; breakwaters block littoral transport and cause deposition/erosion and possible harbor silting; jetties keep channels open but widen updrift beaches and starve downdrift beaches.

15. **How do beach nourishment and coastal zone bioengineering work, and what are their limits?** Beach nourishment adds sand to create a positive beach budget (Miami Beach added ~18 million m³ and produced a 200 m beach), but it is expensive, must be repeated, and is quickly removed by large storms. Bioengineering uses plants (dune grasses, Sargassum seaweed, palm roots) for low-cost, environmentally compatible erosion control, but it is still being tested and provides only a weak first defense.

16. **How do adaptive management, integrated coastal zone management, and E-lines/E-zones reduce coastal risk?** Adaptive management uses science and modeling to reduce uncertainty and adjust as conditions change; integrated coastal zone management maintains ecological function and reduces user conflicts; E-lines/E-zones map expected erosion and set setback distances, keeping development out of imminent-hazard areas and requiring pilings for structures seaward of the E-60 line.

17. **How do perception and proximity to the coast influence adjustment to coastal hazards?** People who live in the immediate hazard area tend to be well informed and see erosion as a serious threat; those a few hundred meters away know little about its frequency or severity; and those farther inland barely perceive it as a hazard. Many people also fail to recognize rip currents and plunging waves as dangers.

18. **How do the Folly Island, Ocean City/Assateague, Cape Hatteras, and Pointe du Hoc examples illustrate the interaction of natural processes and human decisions?** **Folly Island:** the Charleston jetties blocked sand drift, causing severe erosion; responses included groins and seawalls (which worsened erosion), lawsuits, and repeated beach nourishment. **Ocean City/Assateague:** Ocean City inlet jetties starved Assateague, causing ~11 m/yr erosion while beaches north widened. **Cape Hatteras:** managed retreat successfully moved the lighthouse 800+ m inland. **Pointe du Hoc:** a value judgment to preserve a historic site led to a site-specific, temporary hard solution (filling sea caves) rather than retreat.

## Answers to Practice Questions

1. **Define coast, barrier island, sea cliff, bluff, spit, and littoral cell.** Coast: the dynamic zone where sea meets land. Barrier island: a long, narrow sandy island separated from the mainland by a lagoon or bay. Sea cliff: a steep cliff along the seashore produced by wave erosion. Bluff: a similar steep slope along a lakeshore. Spit: a sandy peninsula extending from the mainland into the water. Littoral cell: a coastal segment (system) with linked sand sources, transport paths, and sinks.

2. **Explain how plate tectonics and climate influence coastal morphology in North America.** Passive (east, Arctic) coasts have wide shelves, barrier islands, and sandy beaches; active (west, Hawaii, Puerto Rico, Virgin Islands, southern Alaska) coasts have sea cliffs and rocky shorelines from mountain building. Climate adds ice-affected shores in Alaska/Canada and the Great Lakes, marsh vegetation in temperate regions, and mangroves in subtropical regions.

3. **Describe the three factors that control wave size and define wave height, wavelength, and wave period.** Wave size depends on wind velocity, wind duration, and fetch. Wave height is the trough-to-crest difference; wavelength is the crest-to-crest distance; wave period is the time for successive waves to pass a reference point.

4. **Explain rogue waves and how wave energy relates to wave height.** Rogue waves are unusually large waves, formed mainly by constructive interference of multiple waves (and influenced by undersea irregularities and currents), that can endanger ships and people. Wave energy is approximately proportional to the square of wave height, so a 5 m wave has about 25 times the energy of a 1 m wave.

5. **Describe wave refraction and its effects on headlands and adjacent beaches.** Refraction bends wave fronts as they slow in shallow water. Energy converges on headlands (larger waves, more erosion) and diverges along adjacent shores (smaller waves, deposition), so erosion tends to straighten the coastline.

6. **Compare plunging and spilling breakers and identify the beach conditions that favor each.** Plunging breakers (steep beaches) peak and curl and are erosive; spilling breakers (wide, flat beaches) spill gently and deposit sand.

7. **Identify the onshore and offshore features of a beach.** Onshore: sea cliff or bluff, dunes or vegetation, berm(s), beach face, and swash zone. Offshore: surf zone, breaker zone, longshore bars, and longshore troughs.

8. **Explain littoral transport, beach drift, and longshore drift, including typical rates.** Littoral transport is the movement of sediment parallel to shore, comprising beach drift (zigzag movement in the swash zone) and longshore drift (transport by longshore currents in the surf zone). U.S. seacoast longshore drift commonly moves about 150,000-300,000 m³/yr; Great Lakes rates are about 6,000-69,000 m³/yr.

9. **Distinguish eustatic from relative sea level and explain thermal expansion and melting ice.** Eustatic sea level is global, controlled by ocean water volume and basin shape; relative sea level is observed locally and includes land movement. Thermal expansion (about 1.6 mm/yr) and melting ice (about 1.5 mm/yr) together produce the current eustatic rise of about 3 mm/yr.

10. **Describe how tides, weather, storm surge, and El Niño change sea level over short periods.** Astronomical tides (Moon/Sun) cause daily/seasonal changes; wind speed and atmospheric pressure change water level over hours to days, with storm surge as an extreme case; and El Niño can change sea level by up to ~30 cm over days to months.

11. **Identify major regions at risk from coastal hazards and typical erosion rates.** All 30 U.S. states and Canadian provinces bordering the ocean or Great Lakes. Southeastern barrier islands average 0.3-1.0 m/yr (up to 8 m/yr); Florida/Gulf 0.3-2 m/yr; Great Lakes 0.3-1 m/yr (up to 15 m/yr); West Coast 0.1-0.3 m/yr. Low passive coasts (Long Island to Florida, Arctic Canada, Alaska North Slope) and atolls (Marshall Islands, Micronesia, Palau) are most threatened by rising sea level.

12. **Explain how rip currents form and describe how to escape one.** They form when large waves pile up water that escapes offshore through gaps in the longshore bar. To escape: don't panic, swim parallel to shore until out of the current, then to shore; if unable, wave and yell for help.

13. **Explain the beach budget and how a dam can change it from positive to negative.** The beach budget balances sand inputs (littoral transport from updrift, cliff/dune erosion, rivers), storage, and outputs (littoral drift away, storm return flow, wind). In the textbook example, the budget before a dam was +6,500 m³/yr (net growth) but after the dam cut river sediment it became -5,500 m³/yr (net erosion).

14. **Describe sea cliff and bluff erosion and the human activities that accelerate it.** They erode by combined wave action and land processes (runoff, landslides). People accelerate erosion by increasing surface runoff (urbanization), increasing groundwater discharge (watering lawns), and adding weight on top (houses, walls, pools).

15. **Trace linkages among coastal processes and earthquakes, tsunamis, cyclones, flooding, landslides, and subsidence.** Earthquakes/volcanoes/tsunamis reshape shorelines; cyclones bring surge, waves, and coastal flooding; subsidence increases flood/surge vulnerability; wave erosion undercuts cliffs and triggers landslides; and climate change/sea-level rise increase storm energy and erosion.

16. **List the natural service functions of beaches and coastal processes.** Sand transport/storage; sediment supply to lagoons, estuaries, and dunes; wave-energy dissipation; pollutant breakdown and nutrient cycling; wildlife habitat; groundwater filtration; biodiversity; food sources; scenic/aesthetic value; and recreation.

17. **Explain how barrier-island development and coastal engineering can increase erosion (Ocean City/Assateague example).** High-rise development and dune removal increased hurricane vulnerability at Ocean City, and the 1935 inlet jetties blocked southward sand drift, starving the north end of Assateague Island (~11 m/yr erosion) while widening beaches north of the inlet.

18. **Compare the causes and effects of seawalls, groins, breakwaters, and jetties.** Seawalls (parallel to shore) reflect wave energy and promote narrower beaches; groins (perpendicular) trap sand updrift and erode downdrift; breakwaters (offshore) block littoral transport and cause deposition/erosion and possible harbor silting; jetties (pairs at inlets) keep channels open but widen updrift beaches and starve downdrift beaches.

19. **Describe beach nourishment and coastal zone bioengineering, with their advantages and disadvantages.** Beach nourishment adds sand to create a positive budget (Miami Beach: ~$62 million, ~18 million m³, 200 m-wide beach); advantages are aesthetics and recreation, disadvantages are cost, repetition, sand-source issues, and storm loss. Bioengineering uses plants (dune grasses, Sargassum, palm roots) for low-cost, natural-looking erosion control, but it is still being tested and provides only a weak first defense.

20. **Explain adaptive management, integrated coastal zone management, and the use of E-lines and E-zones.** Adaptive management uses science/modeling, promotes sustainability, communicates alternatives, and changes as conditions change. Integrated coastal zone management maintains ecological function and reduces user conflicts. E-lines show expected erosion at future times (E-10 = 10 years) and E-zones define setbacks: no permanent structures seaward of the E-60 line, movable structures in intermediate/long-term zones, and pilings for new structures seaward of E-60.

21. **Explain how perception of coastal hazards changes with proximity to the coast.** People in the immediate hazard area tend to be well informed and perceive erosion as serious; those a few hundred meters away know little about frequency/severity; and those farther inland barely perceive it as a hazard. Many also fail to recognize rip currents and plunging waves as hazards.

22. **Use Folly Island, Cape Hatteras, or Pointe du Hoc to explain how science and human decisions affect coastal losses.** **Folly Island:** the Charleston jetties (1896) blocked sand drift, causing severe erosion; responses included groins and seawalls (which worsened erosion), a lawsuit, and repeated beach nourishment (1979, 1993, 2005, 2014), with the 2014 sand partly removed by Hurricane Joaquin in 2015. **Cape Hatteras:** rather than trying to hold the eroding shoreline, authorities moved the 4,400-ton lighthouse more than 800 m inland in 1999, buying 50-100 years of safety. **Pointe du Hoc:** a value judgment that the historic site must be preserved led to a temporary hard solution (filling sea caves with concrete and using rock bolts, ~$6 million) aimed at reducing retreat by about half, with maintenance anticipated.