The River Lod is a short river draining about 52 km2 (20 sq mi) of north west Sussex. The main source is on the Greensand Ridge at Marley Heights near Haslemere, about 140 metres (460 ft) above sea level. From here it flows west past Lynchmere, then south to Furnace Pond, where iron cannon were cast during the English Civil War. It then turns south east, flowing south of Fernhurst to Lickfold and Lurgashall where it formerly powered Lurgashall Mill, now moved to the Weald and Downland Open Air Museum. From Mill Farm it heads south between high banks, which it only overflows after the heaviest of rainfalls, passing between the hills of Lodsworth and River to Halfway Bridge on the A272 road then joining the River Rother at Lods Bridge.

The Greensand Ridge, also known as the Wealden Greensand, is an extensive, prominent, often wooded, mixed greensand/sandstone escarpment in south-east England. Forming part of the Weald, a former dense forest in Sussex, Surrey and Kent, it runs to and from the East Sussex coast, wrapping around the High Weald and Low Weald. It reaches its highest elevation, 294 metres (965 ft), at Leith Hill in Surrey—the second highest point in south-east England, while another hill in its range, Blackdown, is the highest point in Sussex at 280 metres (919 ft). The eastern end of the ridge forms the northern boundary of Romney Marsh.