The first gauging station on the Mole is south of Gatwick Airport ( above OD). The mean flow is and the river ran dry at this point for the first time in the summer of 1995. The Mole runs under the airport runway in a culvert completed in 1985. The course of the Mole within the airport perimeter has been altered several times since commercial flights began in 1945; however the meanders visible on the 1839 tithe map in the stretch immediately north of the runway were reinstated in 1999, in a £1.2 million project to facilitate airport expansion.