The Derwent Road Floodwash is owned by Wandsworth Council, and along with the surrounding estate, used to form part of Battersea New Cemetery (now Morden Cemetery).
Wandsworth proposed that Merton Council designate it a Local Nature Reserve as far back as 2003. During this time the site seems to have gone backwards, with only one of the five ponds dug in 1999 surviving. That said, it is a Borough II Site of Importance for Nature Conservation, and is something of a hidden secret.
As a flood storage area for the Pyl Brook that runs past it, the Derwent Floodwash can be transformed after heavy rain. Little Egret are regular on here, and the scrub around the site also makes it a good spot for summer species such as Chiffchaff, Blackcap, Whitethroat, and Lesser Whitethroat. The Pyl Brook has breeding Moorhen and Grey Wagtail, and is important as a refuge for Snipe and Green Sandpiper. The flower-rich wet grassland has species uncommon to London, and it is a patch hotspot for grasshoppers, butterflies and dragonflies.
Sparrowfeld Patch 