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| | Geografia d'Europa: material de suport |
 | | Its northern edge lies along the southern catchment boundary of the Upper River Colne and the northern catchment boundary of the River Roding, with the sections in between cutting across the Rivers Thames, Colne and Lee sub-parallel to the Chalk outcrop pattern. |
 | | Its principal tributaries within the area are the rivers Colne, Brent, Lee, Roding, Beam and Ingrebourne which drain southwards and the rivers Wey, Mole, Ravensbourne, Wandle, Beverley Brook, Chertsey Bourne and The Cut which drain northwards. |
 | | It is possible that the river has eroded the London Clay sufficiently to allow a passage for some recharge from the surface through fissures, scour holes or even abandoned boreholes. |
| www.ub.es /medame/lond-bas.html (3895 words) |
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