SO422 Nearshore Oceanography

Spring 2009 Exam 2

 

††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††† Name _________________________

 

 

 

Read all questions carefully.† The definitions should be a complete sentence that fully explains the term.†† For the short answer questions insure that your answer is complete and concise, uses appropriate terminology, shows that you understand any terms used, and covers the key points.† The quality of your answer is critical, and not just a vague general understanding of concepts.

 

Problems††††††††††††††††††† 20† ________

 

6 definitions @5††††††††††† 30† ________

 

5 short answers @10†††††††† 50† ________

 

 

TOTAL††††††††††††††††††††† 100† ________

 

All work on this exam is individual.† You may not any materials (books, notes, computers), and you may not use IM, texting, talking, or any other means to communicate with other individuals.

Note that you must answer 5 of the definitions and 5 of the short answer questions, but your only choice on the short answer is which of the two aerial views to discuss.†

 

L = (g T≤ / (2 p)) * tanh ( 2 p D / L )

D / L=† D / L * tanh ( 2 p D / L )

umax = p H / (T sinh(2pd/L))

KR = ÷(cos a / cos a)

C1 sin a = C sin a1

V = 1.18 * sin(ab) cos(ab) * (÷(gHb))

V= 0.58 * sin(2*ab) * (÷(gHb))

H/D = 0.78

 

Phi†††† =-log2(Dia mm/1mm)

logx(a) = logy(a)/ logy(x)

(Mean - Median) / Std Dev

Normal Distribution: 1 s from Mean at 16% and 84%

sin(2*a) = 2 * sin(a) cos(a)

 



1. Problem (20 points):

 

The following sand (sample 6216311, p.B49, Technical Report CERC 92-7) was collected at Duck, North Carolina:

Phi Size

Weight Percent

 

 

-2

0.000

 

 

-1

0.081

 

 

0

0.692

 

 

1

4.029

 

 

2

3.980

 

 

3

81.949

 

 

4

9.269

 

 

Pan

0.000

 

 

(2) List the parameters that define the best fitting log-normal distribution for this or any other sand samples.

 

 

 

 

(2) Calculate the parameters, and only the parameters, that define the best fitting log-normal distribution for this sand.

 

 

Mean= 2.50 Sigma (Std dev)= 0.37  

 

(4) How would increasing each of these parameters affect your graph on the next page?

 

 

 

 

(4) Calculate the parameter that determines how well this sand fits the log-normal distribution, and compare that result with a graphical measure.

 

 Alpha (skewness)= 0.00
 

 

(4) What is the size in mm of the median sand size?

 

 

Median = Phi50= 2.50=0.18 mm

 

 

(4) The sand we will used in the wave tank had a median size of 0.32 mm.† What is this size in phi units, and what percentage of the sand from Duck is larger than this size?

 

0.32 mm = 1.64 Phi.  Come up at phi=1.64, intersect the curve, and then go over to the horizontal axis at about 7%, which is the percentage of the Duck sand that is larger (because small phi sizes on the left are large sand grains).


 

Phi16= 2.14 Phi50= 2.50 Phi84= 2.87
 


 

 

Definitions: with a single complete sentence, define 6 of the following terms.† Show that you clearly understand the concept involved.

 

        Rollover:

        Closure depth:

        Sink:

        Isostatic sea level rise:

        Reflective profile:

        Trough:

        Rip tides:



There are 5 short answer questions in part 3.† You must answer 4 of them.† Each is worth 10 points.† For full credit you must cover the important topics and use the correct terminology.

 

†1.† †The two diagrams below show twentieth century sea level curves for two locations.† Comment on the following points:

        Are these records accurate for determining what is going on at the location;

        What differences can you see between the two records;

        Why can different locations have different trends for sea level during the same time interval;

        Suggest where each of these locations might be.

 

 

 


Tide stations (these are pretty extreme in magnitude:

 


 

2.† The diagram below shows two surveys of a beach in North Carolina done 5 days apart (dates in the upper right corner).† Discuss:

 

.


 


3 and 4. †For two of the next three aerial images, describe what features you see in the image, how those features form, and what processes are going on in the nearshore environment.† If you can assume a direction for currents, waves, or tides, indicate how you can infer the information.† Do not make any assumptions about the direction of north.† (10 points each)

 

Sandy Hook, NJ (spit and longshore current)

 

 

 

Near Monterey, California embayment and wave angle of attack

 


 

North Carolina pass and tidal delta

 

Insure that you only answered 2 of 3 questions on the previous images.

 


 

 

5.† What does this diagram attempt to show, and why is this subject of such intense interest to coastal engineers and oceanographers? (10 points)

 

This was Komar Figure 4-40