144 



FLOODS AT THE MANOHESTEB WATERWORKS 



pened that a single heavy flood or fall of rain has been so 

 accurately observed. This fact is my apology for endeavour- 

 ing to place the particulars on record. 



In the early progress of the formation of the embankments, 

 provision was made at each reservoir for the passage of 

 the floods by the construction of a capacious cut or canal 

 called a flood-watercourse, above the level of the reservoirs, 

 as already described. This provision was adopted and em- 

 ployed for the purpose intended both at the Woodhead and 

 Torside Reservoirs, until the embankments at each place 

 were advanced to a height at which it was deemed safe to 

 dispense with the aid of the watercourses, and to depend for 

 safety upon the storage which the reservoirs afibrded, and the 

 means of discharge provided by the two lines of 4 feet pipes 

 which had been introduced in all the embankments. It was 

 necessary also, as the work advanced, to cut across or destroy 

 the watercourses for the purpose of completing what are 

 technically called puddle trenches, which are deep trenches 

 of retentive material, sunk for the reception of the clay or 

 puddle employed to render the whole water-tight. The per- 

 manent waste weirs of the reservoirs also had to be con- 

 structed on the site of the flood water-channels, for which 

 purpose likewise they had to be dispensed with. 



The Rhodes Wood Reservoir, the lowest of the three, 

 would have been similarly provided with a bye-channel for 

 the waste water, but delay had unavoidably arisen by the 

 channel to be formed over an ancient land-slip. This land- 

 slip was well known, and had been long moving slowly. At 

 the turnpike road on the north side of the valley, it had 

 moved about three feet in thirteen years ; but the speed of 

 its motion was materially increased on being cut into for the 

 purpose of forming the watercourse. Means had to be 

 resorted to for arresting its further progress, and the work 

 was consequently so much delayed that this watercourse is 

 not yet completed. 



