IMPROVEMENT OF THE KARACHI HARBOUR. 137 



in the following year this was supplemented by building a bank ; rising 

 5 feet above low-water level, across the Chinna creek outlet ; in 187 1 

 this bank was raised to 6i ft. above low water, and in 1873 the 

 opening was completely closed and has remained so ever since. In the 

 harbour the first effect of this was disappointing, for the currents of 

 the tidal scour — which had attained a condition of equilibrium — were 

 interfered with, and one of the first effects of the fresh scour set up 

 was to form a deposit in the deep water of the harbour. But just as 

 the currents soon worked out a fresh condition of comparative stability 

 after the formation of the Napier mole, so the period of instability 

 consequent on the opening of a passage through it soon passed away, 

 the channels resumed a condition of equilibrium and the harbour 

 experienced the effect of the increased tidal scour. At present the 

 channels would be in a state of epuilibrium between force exerted and 

 work to be done, and in a state of general stability accompanied by 

 minor variations in detail, but for the fact that, as the channels so 

 formed would not give sufficient accommodation, the harbour has to 

 be kept open by continuous dredging, and the depth so maintained, 

 being greater than that due to a condition of equilibrium, is constantly 

 being reduced by silting up. 



Outside the harbour the closing of the Chinna creek had the effect 

 of putting an end to the tidal scour which had kept the Clifton fore- 

 shore free from sand, and a survey made in 1876 l shows that all trace 

 of the old tidal channel had been obliterated and the low-water mark 

 bent round with an even curve in front of the old Chinna creek. 

 Since then the foreshore has advanced, coming closer and closer to the 

 final curve, along which the tidal and other currents will sweep the 

 sand, neither eroding nor adding to the foreshore. At present the 

 shore line lies nearly half a mile from the embankment across the 

 Chinna creek and the backwater is separated from the sea by a 

 tract of sanddunes, while the effect of the advance of the shore line 

 is seen on either side, and extends— as has been mentioned— to beyond 

 Clifton. The actual area which has been added to dry land cannot be 



See Plate V. 



( 5 ) 



