The correct answer to this question is option 1, a sand bar. A sand bar is a gently sloping accumulation of coarse alluvium deposits that forms in a braided stream.

Let`s dissect the other options to better understand why they are not the correct answer.

Option 2: An alluvial fan is a fan-shaped deposit of sediment that forms at the mouth of a canyon or valley. It is formed by the deposition of sediment carried by a stream as it flows out of the confined space of the canyon or valley and onto a flat surface. This does not match the description of a gently sloping accumulation of coarse alluvium deposits by a braided stream.

Option 3: A bajada refers to a series of coalescing alluvial fans that form along the base of a mountain range. It is formed by the deposition of sediment carried by multiple streams flowing down from the mountains. Again, this does not match the description given in the question.

Option 4: "Diaras" is not a recognized term in the context of fluvial geomorphology or river systems.

In conclusion, the correct answer is option 1 because a sand bar is the term used to describe the gently sloping accumulation of