LII. J. I. HAYCROFT. 



dealt with ; and as regards the western suburbs, considering the 

 general nature of the soil and the fact that it is maximum rain- 

 fall which has to be provided for, as a general rule the coefficient 

 should be a maximum ; the mode of occurrence of maximum 

 rainfall must be considered, as already pointed out, viz., during 

 the continuance of what may be classed as moderate rain, which 

 latter, however, tends to saturate the ground, so that the maxi- 

 mum rain should be considered as falling on impermeable surface. 

 Even in the eastern suburbs, where the soil is sandy, and whilst 

 in its natural condition calculated to absorb more than the soil 

 of the other suburbs, still the coefficient should be high. The 

 writer's practice, in such a case, has been to take unity as the 

 coefficient, making an allowance in the extent of the catchment 

 according to the nature of the dwellings erected, as, for instance, 

 a catchment thickly built on, with terraces and asphalted yards, 

 would be treated as impermeable, whilst an area of equal extent, 

 on which detached residences with gardens, etc., predominated, 

 would have a lower coefficient. 



As regards the rate of rainfall, greater diversity of opinion 

 exists. A rainfall at the rate of six inches per hour should be 

 provided for, and has been used in the writer's practice for 

 Sydney and suburbs. On many occasions, in the courts of this 

 colony, it has been maintained that it is sufficient to provide for 

 a rainfall at the rate of two inches per hour, with only 50 per 

 cent, of that flowing otf areas under 20 acres in extent. 



What local authorities have to guard against is, that damage 

 to property does not accrue from insufficient provision for flood 

 water, caused by rain other than that of a phenomenal nature, 

 and this less allowance, viz., for 2 inches, has been found 

 inadequate. 



Now, it is known that rain does fall from time to time in 

 the neighbourhood of Sydney at the rate of 6 inches per hour, 

 and should therefore be provided for, since it cannot be classed 

 as phenomenal. 



Chief Justice Darley, as reported in " Browning's Municipal 

 Digest," has spoken as follows on this point : — "'Phenomenal' 



