Between 1842 and 1847 an extraordinary and total change took place in the Cottenham landscape. The enclosure involved the breaking up of the commons and open fields into distinct parcels, privately owned, fenced or ditched. The fens were drained, centuries old paths were blocked and replace by a new, but much reduced, network of tracks. Land which hadn't been ploughed since Roman times was cultivated again. Maps showing the old and new divisions of land make it clear that for the most part the old furlong boundaries were not retained and only the boundaries formed by the established roads in the south of the parish survived largely unaltered. In the words of one contemporary: 'now a great change came over Cottenham... Old times were to pass away and all things to become new... nearly all the old landmarks were removed.'
It was a traumatic time 'in the Spring 1843 commenced the breaking up of the Fen... one mass of smoke used to be burning all night and day.' Owners of land in the open fields and common grazing rights all received new parcels of land proportional to old holdings, but those who had only let their properties lost their common rights and had to survive as agricultural labourers. The whole process was also very expensive, and for many it must have been years before the investment really paid off - perhaps for some of the smaller landholders it never really did and they were forced to sell out to their more prosperous neighbours. Miles of new hedgerow were now necessary to keep stock in, and it was the responsibility of the new owners to protect it from grazing while it became established and then maintain it.
There were now two distinct drainage networks, which kept the parish safe from flooding in all but the most exceptional times. The Old West River and the Lode carried water from upstream quickly through the parish; these were protected by high banks and often flowed at a level well above that of the surrounding land (which in peaty areas shrank as it dried out, making drainage even more difficult). The new enclosed fields often had a network of clay field drains (made in the local brickworks) installed, which fed water into ditches, which in turn emptied into larger 'engine drains'. These led to steam powered pumping engines at Smithey Fen and Chear Fen, which raised the water into the Old West River. Water which leaked through the banks was caught in smaller 'sock' drains running parallel to the river, and pumped back up.
With some additions, the drainage network is essentially the same today (see map [link to drainage map]), although diesel pumps have replaced the steam engines. With the possible exception of stretches of Reynolds Ditch and Clay Ditch on the south-west and south-east boundaries of the parish, none of the watercourses in Cottenham follow a 'natural' course. Even the Old West River is the result of the original course of the Ouse diverting into the Car Dyke and then finding a new route to join the Cam. These deep and straight ditches form significant features in the landscape; in fact in large parts of the parish they are arguably the only significant features. The high banked rivers are also visually significant, but quite distinct; paths along the top of the banks make up a significant proportion of the footpaths in the parish.