For the 1997 "River Taw" series she worked at night, placing photographic paper on the river bed and allowing the images to be exposed through ambient light, aided by the use of a flash gun. Using the river near her Devon home as a lens, Derges captured fragments of ivy, ice, and debris reflected in or passing through the water. Her technique involved a very direct and unmediated physical relationship with the landscape, while her "Under The Moon" series involved working with photographs of the moon and combining these with water and branch patterns exposed to sound vibrations in the darkroom.