Sir, how the sand dunes start forming from leeward side?. 2. are leeward side and steeper side are same thing.?

then, why there is accumulation of sand on opposite side of wind ( in my book page)?

sand is accumulated like a mound but from the stoss side it is eroded so it appears like deposited on the leewardside. Also due to pressure difference.its on the Lee side steep

There are several types of dunes depending on the shape . Longitudinal dune, transverse dune, parabolic dune,star dune, barchan,seif

Dear student, ask me in case of any doubt.

sir how the sand dune formation begin...(as book says it starts on leeward side of obstacles and aftr deposition it itself become obstacle. ) i m asking about beginning

how process starts.

For the beginning of sand dunes formation, you need specific flow velocity for a specific grain size. When flow velocity increases the threshold speed, sands start piling up lead to the formation of sand dunes. Dunes have two sides, stoss and Lee. Due to flow of water, sands on stoss side gets eroded and deposited on lee side. Sand dunes grow on lee side by this process. I hope this helps.

sir, in question i send i diagram, what is fencing post in it.

Fencing post is something that prohibits the erosion of sand from stoss side. You can look at the figure, I attached in my answer instead of mentioned in the book.

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