 However the lock has in fact rarely been used by freight barges.In August 2013, a long period of hot dry weather followed by heavy rain washed polluted road run-off water into the Lower Lea, causing deoxygenation of the water.The role of the canalisation of the Bow Back Rivers in and around the Olympic Park, with its consequences for tidal flow have been implicated in the considerable levels of fish kill which resulted from the incident.