1861.] Note on the Rain-Fall in the Mahamddy Basin. 221 
2nd. The maximum average rainfall in the basin has not been 
ascertained, hut it is probably as much as 90 inches, possibly more. 
3rd. The maximum annual discharge of the river is about four 
billions cubic feet. 
4sth. The maximum flood discharge between the Passes and the 
Delta, is 21.00,000 cubic feet per second. 
5th. The maximum flood discharge at the head of the Delta is 
(not less, possibly somewhat more than) 1,800,000 cubic feet per 
second. 
6th. The Delta channels (more or less embanked as they are) are 
able to pass off only one-half of the volume of a maximum flood ; or 
900,000 cubic feet per second. 
7th. The occurrence of a maximum, or “ very extraordinary flood 
is dependent on the contingency of an average fall of 9” of rain 
taking place over the whole area of the basin in a single storm, 
whilst the river is well filled by previous heavy rain. Such an occur- 
rence may be looked for possibly once in twenty years. 
8th. The effect of such “very extraordinary” flood is to carry 
away from 25 to 30 linear miles of the embankments of the Delta. 
6th. “ Extraordinary” floods, the necessary effect of which is the 
destruction of ten linear miles or so only, of embankments may pos- 
sibly recur five times as often as the above. 
Of the remedy which can be applied, I have written so fully in my 
Report, Part III. Cuttack Rivers’ Survey, that I need not here say any 
hing further regarding it, saving that I continue strong in the belief 
that the Mahanuddy can be rendered powerless for evil, by the con- 
struction of the proposed dam at Kundlepore, and the excavation of 
the proposed cutting at Daltollah, through the Mahanuddy’s eastern 
water-shed ; at a money outlay of about a quarter of a million sterling, 
md after an outlay of time which I shall be better able than at present 
:0 estimate, when I receive from the Government of Bengal the infor- 
mation regarding the formation of the Yergel River in Ceylon, as a 
branch of the Mahawelligunga River, regarding which 1 have re- 
quested that certain particulars might be obtained from the Ceylon 
Government. 
