One clearly catches runoff and is quite deeply eroded whereas the other is just muddy, for now anyway. The steep slope along the western side of Richmond Park is an old river terrace and, relative to the predominant clay in the area, the sand and gravel deposits drain quite well and make a good place for a walk after wet weather.
Uploaded to Geograph by Hugh Venables on 12 March 2016
Photo © Hugh Venables, 12 March 2016. Licensed for reuse under this Creative Commons licence