I have a small (2' x 4') lake of crushed limestone in my garden (see picture below). The Japanese inspired garden is intended to be a small replication of a natural area. The problem is that mulch/debris washes into my "lake" during rains. I would like to prevent this to ease maintenance (as you can see, I have failed to clean up the leaves-sorry). I was thinking of lining the "shore" with sonething that would form a lip to catch the debris. I have seen tiles used in this way in Japanese gardening books, but they do not look natural. Perhaps the right size river rock could be used as a surround, or cut/chip native stone to scale and imbed it.

Another thought is to plant small plants all around it like small lilyturf or a varieties of sedum.

I would appreciate ideas. Thank you