Many Hazard City residents have purchased second homes, cottages, or timeshares

Question

Many Hazard City residents have purchased second homes, cottages, or timeshares near the beach. The most popular locations for these purchases are along the ocean beachfront. Potential buyers must be cautious when purchasing properties close to a beach because shoreline erosion can be a significant problem. Therefore, the most prudent buyers seek professional advice before they commit to such an important purchase.

Shoreline erosion is a significant problem, and each year it destroys or damages millions of dollars' worth of property. However, those who are well informed about how erosion occurs are usually willing to research the history of a property and can generally determine if it is at risk. In an effort to minimize such risks for their clients, a Hazard City real estate office has asked you to assess a few properties and report on how they might be affected by shoreline erosion.

Assessment of shoreline property must begin with knowledge of the forces at work: When assessing shoreline-erosion risk, you must keep in mind that moving water will always carry as much sediment as its velocity will allow. The faster the water’s velocity, the more sediment (and larger sediment particles) it can carry. Longshore current occurs when waves approach a beach at an angle. The waves retreat perpendicular to the shoreline, and so sediment is transported along the shoreline. Shoreline protection devices such as groins, rip-rap, and breakwaters disrupt the longshore current’s ability to transport material.

To complete your work, you will use the links on the left, which will help you

·         Understand that shorelines are dynamic locations with erosion and deposition working to alter the landscape;

·         Have some knowledge of shoreline erosion, sediment budgets, and streambank erosion; and

·         Understand the principles that are used to determine if a shoreline property has an erosion hazard.

Part A - Shoreline property assessment

It is time to assess the properties by figuring out how they might be affected by shoreline erosion. Determine the risk status of the following properties by using your knowledge of the factors discussed earlier and information that is found at the Shoreline Erosion and Streambank Erosion links to answer the following question.

Drag the appropriate labels to their respective targets.

Part B - Protecting beaches with groins

At Site 1, three groins are constructed. What would happen to the beach if the middle groin were not constructed?

Choose from part 1, 2, 3, 4.

1. There would be more deposition between the two remaining groins.

2. There would be less erosion between the two remaining groins.

3. There would be more erosion between the two remaining groins.

4. It would have no effect.

Part C - Closely spaced groins

At Site 1, three groins are constructed. What would happen to the beach if five groins were constructed over the same distance?

Choose from part 1, 2, 3, 4.

1. The width of the beach will grow everywhere, but more significant erosion will occur on the downcurrent side.

2. There would be no difference because the groins are already spaced so closely together.

3. The houses next to the groins would be negatively affected due to all the loosely consolidated shifting sand located nearby.

4. The width of the beach would shrink due to excessive erosion.

Part D - Breakwaters and beaches

Breakwaters are constructed to protect a portion of beach from wave action. Over time, how might breakwaters become obsolete (essentially, no londer be needed) for a section of beach?

Choose from part 1, 2, 3, 4.

1. Breakwaters could not become obsolete due to regular beach activity.

2. The sand could build up behind the breakwater so much that the beach connects with the breakwater.

3. The breakwaters could cause storms to slow down just over the protected beach and preferentially destroy any ships moored there.

4. So much erosion could eventually occur downcurrent from the breakwater that the protected beach would be exposed.

Part E - Rivers and beaches

The Clearwater River reaches the ocean just north of this beach. How might damming the Clearwater River affect beach dynamics?

Choose from part 1, 2, 3, 4.

1. Damming the river would decrease the amount of sediment reaching the beach and cause the beach to shrink.

2. Damming the river would have no effect on the beach, since rivers do not carry sediment.

3. Damming the river would have no effect on the beach, since beaches are formed due to wave action.

4. Damming the river would increase the amount of sediment reaching the beach and cause the beach to grow.

Part F - Picnicking at the river

You are taking your family for a picnic along Muskett River. As you are trying to determine where to picnic, your priority is to place your family on the side of the river where the water is moving the slowest. Where should you set up your picnic?

Choose from part 1, 2, 3, 4.

1. On the opposite side of the river from a point bar

2. Along a straight portion of the river

3. At a point bar

4. It doesn't matter; all the water moves at the same velocity.

Part G - Placing rip-rap in a river

Riprap can reduce the velocity (hence the energy and carrying capacity) of the water in the river. How might placing a rip-rap along a streambank affect the beach where the stream meets the ocean?

Choose from part 1, 2, 3, 4.

1. More deposition could occur, because the stream will preferentially drop its sediment at the rip-rap.

2. The rip-rap will cause the water to slow down when it reaches the ocean, causing more erosion at the beach.

3. More erosion could occur, because the stream is carrying less sediment for its velocity than it should.

4. Rip-rap along a stream will not affect the beach, because the two are not related.

Part H - Erosion rates

The Island Migration Case Study shows how Brown's Island in the Ohio River has migrated over time. The original map was published in 1954. The photo revision took place in 1983 and showed that the northern end of the island had eroded 5 feet (60 inches) over that time. At what rate was the northern end of Brown's Island eroding during that period?

Choose from part 1, 2, 3, 4.

1. approximately 5 feet/year

2. approximately 2.5 feet/year

3. approximately .5 inches/year

4. approximately 2 inches/year

Part I - Erosion of Brown’s Island

If Brown's Island were migrating at 1 foot/year, how long would it take to erode the entire length of the island?

Choose from part 1, 2, 3, 4.

1. almost 13,000 years

2. not more than 200 years

3. over 20,000 years

4. between 900 and 1000 years

Part J - Erosion of Clayton Point

At what rate did the northern side of Clayton Point (Site 2) erode between the two maps provided?

Choose from part 1, 2, 3, 4.

1. between 6 and 7 feet/year

2. over 20 feet/year

3. less than 5 feet/year

4. between 90 and 100 feet/year

1. There would be more deposition between the two remaining groins.

2. There would be less erosion between the two remaining groins.

3. There would be more erosion between the two remaining groins.

4. It would have no effect.

Drag the appropriate labels to their respective targets safe at risk SITE 1 SITE 2 Site 1: Simpsorn Site 2: Carter Three new 1. groins under construction 2. Site 2: Froughton Clayton Point Clayton Point 1988 3. 2003 Site 1: Klaste- 100 feet 60 feet 60 feet SITE 3 SITE 4 Site 3: Property 2 -Site 4: Randall Muskett River (Flowing towards the northeast) Site 3: Property 1 Recently placed rip-rap Site 4: Wilson- 100 feet 100 feet e Windows oto Settings to activate W reset? help Submit Hints My Answers Give Up Review Part

Explanation / Answer

Part A: Insufficient data

Part B: Answer 1

Part C: Answer 1

Part D: Answer 2

Part E: Answer 1

Part F: Answer 3

Part G: Answer 2

Part H: Answer 4

Part I: Insufficient Information-Length of Brown's Island not given

Part J: Answer 1

Explanation:

Total Erosion approximately 120 Feet in 2003 - 1988 = 15 years. Thus, erosion rate =120 feet /15 years = 8 feet/yr. Closest figure given in Answer 1.

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