George :

Think about what your beds were like when water was up. Beds on bottom with weeds around them. The 2 places colony spawners like BG/RES will avoid are locations with lots of silting and places with "thick" weeds where little or no light will penetrate. They will spawn in normal weeds and IMO prefer hard clay/gravel locations very near or interspersed amongst weed beds. They are survivors and will spawn in the best location they can find and will adapt to the situation.