198 Modern Drainage Problems 



The area covered by the Internal Drainage Districts is approximately 

 276,063 acres, with an annual value, for drainage rates, of about ^{^63 5,000. 

 These Internal Drainage Boards, which number 90, are responsible for 

 local drainage. 



The total mileage of main river for which the Board is responsible 

 amounts to about 500 miles, of which 306 are in the Upland Area, and 

 190 in the Fenland itself Work in the Upland Area rivers is similar to that 

 carried out by other Catchment Boards, but with the strict necessity of 

 bearing in mind the fact that these rivers discharge into the Fenland. In 

 upper Cambridgeshire, the Board is responsible for the Rivers Cam and 

 Rhee, which are now kept in as satisfactory a state as the funds wiU permit. 

 The fenland areas are roughly at Ordnance Datum level, and the upland 

 streams are carried through tliis area as embanked rivers above the level 

 of the land on either side. The Internal Drainage Boards have, therefore, 

 to pump the water up into the river above their own ground, and the 

 pumps must be capable of lifting to a height sufficient to reach the flood 

 levels witliin the banks. 



THE MIDDLE LEVEL 



The Middle Level hes between the Old Bedford River and the River 

 Nene (see Fig. 47). It contains 165,000 acres of groimd, of which about 

 120,000 acres are actual fen with 150 miles of main waterways. Most of 

 its fifty Internal Districts discharge by pumping into the Middle Level 

 Drainage System, for which the Middle Level ComiTiissioners are respon- 

 sible. But the area of the Sutton, Mepal, Manea, and Welney Internal 

 Boards has separate pumping stations discharging into a Counterwash 

 drain that runs parallel with the Old Bedford, separated from it by a low 

 bank. This drain has a gravity outfall just below Denver Sluice. 



Some portions of the Middle Level fall to 4 ft. beloii^ Ordnance Datum; 

 and it must be remembered that the high-tide levels outside rise to some- 

 thing of the order of 13 or 17 and even to 18 ft. above o.D. Prior to 1848, 

 the Level discharged by Tong's Drain into the Ouse below Denver; but, 

 on the advice of Messrs Burgess and Walker, a twelve-mile cut was made 

 through Norfolk Marshland, and the Middle Level waters discharged into 

 the Ouse through a new sluice at St Germans, eight miles below Denver 

 Sluice. The cost of this scheme amounted to ^450,000. 



The reduced low-tide levels that resulted from these measures proved 

 satisfactory for many years. In 1862, however, the sluices at St Germans 

 "blew up"; the river banks broke down, and tides flowed up the cut to 

 flood some 6000 acres. Sir John Hawkshaw devised a dam with a series of 



