Achieving logic and coherence depends on moving from one topic to another in a logical sequence and on the use of legitimate paragraphing which allows that logic to be clearly visible to the reader.

A logical flow of information should occur at a number of levels in your writing.

It needs to occur across the WHOLE TEXT

Therefore the movement of information BETWEEN paragraphs should be logical and the movement of information WITHIN paragraphs must also be logical. Logical flow within paragraphs requires the movement from one sentence to another to be logical.