Ok, so I haven't really looked deeply into this subject, but it is something that I think is really interesting and is also a thing I would like to learn and investigate further.
I'm not really sure on if it fits into "biomimicry" but it is about how to handle water.. inspired by how the nature's doing it, the natural processes. The design of urban drainage system may improve the fauna and flora and might aswell contribute to the perception of the urban space if it's done in a creative and inspiring way I think. As written before, I would like to investigate it further, but to begin with I'm posting a link to a wikipeda page about it and also a picture from Västra Hamnen in Malmö where offices such as SLA from Copenhagen worked with urban drainage system in nice way and as a part of the design of the site.
// Karl Tyrväinen