Damp is a negative word used to describe humidity; pretty much like moist, but while moist has a positive connotation (moist is desirable), damp has a negative one (nobody wants to live in a damp house). Brown, on the other hand, is a color associated with sadness, isolation and loneliness. The words “Damp and Brown” in the poem are used by the author to create a visual imagery of a not so pleasant sad beach. The author is using visual imagery to to make the poem more haunting or unsettling.
We can conclude that the correct answer is: to make the poem more haunting or unsettling.
