Black literature is really hard to find in conventional A-Z shelving. A member of a Black reading group in Huddersfield asked for help from the staff on finding Black authors. 'A name like Diran Adebayo, I can tell that's going to be Black, but what about Jackie Kay or Joe Pemberton?'
People who come into the library looking for something specific, books about Black figures in history, for instance, may well not know where to look and they may not ask. How will these readers who are not familiar with library organisation find books by Black writers if they want them? And how can you showcase the work of Black writers to show the range you have?
A separate Black section can be a real help in these circumstances. If you make a separate section you must have enough stock to keep it refreshed. There is nothing worse than a sad collection of tatty out-of-date 'ethnic' material.
If you do not have the stock or the readers to make a separate Black section viable, make sure you regularly pull books off the shelves into promotions to catch the attention of both Black and white readers.