SO422 Nearshore Oceanography
Fall 2005 Exam 2
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 general understanding of concepts.
Problems 30 ________
6 definitions @5 30 ________
4 short answers @10 40 ________
TOTAL 100 ________
Note that you must answer 5 of the definitions and 5 of the short answer questions. Insure that you do not waste time answering more than the required number in each section.
Selected answers shown in red.
L = (g T² / (2 p)) * tanh ( 2 p D / L )
D / L_{¥}= D / L * tanh ( 2 p D / L )
u_{max} = p H / (T sinh(2pd/L))
K_{R} = Ö(cos a_{¥} / cos a)
C_{1} sin a_{¥} = C_{¥} sin a_{1}
V = 1.18 * sin(a_{b}) cos(a_{b}) * (Ö(gH_{b}))
V= 0.58 * sin(2*a_{b}) * (Ö(gH_{b}))
H/D = 0.78
Phi =log_{2}(Dia mm/1mm)
log_{x}(a) = log_{y}(a)/ log_{y}(x)
(Mean  Median) / Std Dev
Normal Distribution: 1 s from Mean at 16% and 84%
sin(2*a) = 2 * sin(a) cos(a)
1. Problems:
The following sand (sample 6216502, p.B52, Technical Report CERC 927) was collected at Duck, North Carolina:
Phi Size 
Wt Percent 
Cum % Retained 
2 
0.020 
0.02 
1 
0.000 
0.02 
0 
2.280 
2.30 
1 
29.232 
31.55 
2 
59.029 
90.61 
3 
9.380 
100 
(2) List the parameters that define the best fitting lognormal distribution for this or any other sand samples.
(2) Calculate the parameters, and only the parameters, that define the best fitting lognormal distribution for this sand.
Mean= 1.24
Sigma (Std dev)= 0.58
(4) How would changing each of these parameters affect your graph on the next page?
(4) Calculate the parameter that determines how well this sand fits the lognormal distribution, and compare that result with a graphical measure.
Alpha (skewness)=0.03
(4) What is the size in mm of the median sand size?
Median = Phi50 = 1.26 = 0.42 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 on the graph this is Phi75, so 75% of the sand from Duck is larger than the median sand from the wave tank
(10). Complete the survey notes for a group at Assateague.
The survey team starts with the rod at BM07 in the parking lot (elev 3.00) and the level halfway to the dune; the reading on the rod 1.63. They then take 3 readings at stations 5 m (reading 1.42), 10 m (reading 1.37), and 15 m (reading 1.21) away from the BM. They then move the level to the top of the dune and take a reading (3.21) with the rod still on the 15 m station.
Station 
B.S. 
H.I. 
F.S. 
Elev 
Dist 
BM07 
1.63 
4.63 

3.00 
0 



1.42 
3.21 
5 



1.37 
3.26 
10 

3.21 
6.63 
1.21 
3.42 
15 
2. Definitions: with a single complete sentence, define 6 of the following terms. Show that you clearly understand the concept involved.
· Ebb tide delta:
· Closure depth:
· Sink:
· Eustatic sea level rise:
· Tidal bore:
· Trough: (could be wave crest/trough, or the offshore bar/trough)
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. We frequently draw beach profiles like the one below to discuss the changes in the shoreline. Is such a 2D depiction sufficient for budget computations and other discussions of changes on the beach?
2. The global rate of sea level rise averages about 23 mm/year, while the rate for Annapolis is about 3.5 mm/year. Why isn’t the rate of sea level rise constant, and are there locations where sea level is dropping?
Sea level rise is not constant, either in time or location on earth.
Sea level rise is always relative (sum of water rise and land subsidence)
There are world wide (eustatic) and local (isostatic) components
The last (Pleistocene) Ice Age explains a lot to current sea level change
3. What does this diagram attempt to show, and why is this subject of such intense interest to coastal engineers and oceanographers?
4. Discuss two significant ways that the coasts of the Great Lakes respond very differently than open ocean coasts like we saw at Assateague.
Tidal effects
Rates of sea level change
Multiple bars.
5. How would you go about creating a budget for a typical coastal cell, and what would you expect to be the major contributors in the main categories?