The sand budget on Jones Beach has a deficit because sand is trapped in Fire Isl

Question

The sand budget on Jones Beach has a deficit because sand is trapped in Fire Island Inlet. If sand is trapped in Fire Island Inlet at a rate of 400,000 cubic yards per year. What would be the expected average rate of shoreline recession due to this deficit over the 70,000-foot shoreline of Jones Beach? Hint: Use the rule of thumb of "one cubic yard per foot of shoreline per foot of beach width"describes in the attachment.

There’s a rule of thumb that tells you how much the shoreline will erode if you’re losing sand or how much wider the beach will become if you add sand.

The rule is “one cubic yard per foot per foot”. This means that it takes one cubic yard of sand to change the shoreline position by one foot for every foot of shoreline length. To use this you need to know any two of the following three numbers:

1.the number of cubic yards added or lost

2.length of the shoreline in feet

3.change in the shoreline position (i.e. the number of feet the shoreline recedes or the number of feet the beach widens).

Example:

If we have a beach 6000 feet long and add 1,000,000 cubic yards of sand, how much wider does the beach get?

“One cubic yard per foot per foot” =             1,000,000 cubic yards/6000 feet/WHAT

We want to put in some value for “WHAT” so that this number comes out to be one.

1,000,000/6,000/WHAT = 1 or WHAT = 1,000,000/6,000 = 166 feet

We can check this by putting in the 166 and recalculating. It does equal one, so it works.

1,000,000/6,000/166 = 1

Got it?

Likewise, if we have a beach 6,000 feet long and let’s say 60,000 cubic yards of sand cave in at one end and 100,000 go out at the other. That is,

                                                  <-----------6000 ft --------à

BEACH

________________________________________________________________________<===100,000 yd 3                     OCEAN          <=== 60,000 yd 3

Then, this beach is losing 40,000 yd 3

40,000 yd3/6000 feet/WHAT = 1 cubic yard per foot per foot

WHAT = 6.6 feet = amount the shoreline will go back

Explanation / Answer

Beach is loosing 400,000 cubic yard per year of sand

Length of shore line of beach=70,000 feet

On applying the rule:

1 cubic yard per foot per foot

4,00,000 cubic yard/40,000 feet/ what

Now,400,000/70,000/waht=1

What=5.7 feet

5.7 feet of shore will recede

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