890 JOURNAL OF FOKKSTRY 



to Stop them permanently a systematic program of reforestation similar to that 

 in our country must be carried out." 



Then, again. Air. T. Pincione, engineer-in-chief of the Hai Ho Con- 

 servancy Bureau, observed : 



"Providing a sufficient outlet to sea of rain water is essential, but the only 

 way to cure the evil of the quick inrush of freshets is to arrest in the mountain- 

 ous regions the sand which causes the silting up of different channels to the sea. 

 It is said that forests can hold on nearly 50 per cent of rain water, so forests 

 by reducing the capacity of channels by 50 per cent will greatly regulate the 

 downflow of water. 



"The Chihli rivers during freshets have an output from 150 to 200 times the 

 output during dry seasons. For instance, the Yung-ting Ho or Hun Ho in dry 

 season has an output of scarcely 1,500 cubic feet of water per second, but during 

 freshets its output rises to 200,000 cubic feet per second. It is evident that if 

 a channel is prepared for this large output it will silt up during dry seasons on 

 account of the meager supply of water. On the other hand, if the channel is 

 good for 1,500 cubic feet, it cannot carry down to the sea 200,000 cubic feet during 

 rainy seasons. Only reforestation is able to prevent this great difference of out- 

 put, holding on nearly one-half of the rainfall during the heavy rains, and giving 

 it subsequently to the channel. Therefore forests can be compared to. a sponge 

 for retaining rainfall and giving it up gradually. Then also we must consider 

 that the vapor from the sea when encountering with forests is bound to con- 

 dense and restitute to the sea the water taken, with a process more uniform than 

 would take place on the bare mountains. 



"Therefore, in my opinion, reforestation is absolutely indispensable for the 

 proper regulation of rainfall and the improvement of the channels carrying the 

 water back to the sea." 



Perhaps the most convincing account of the need of reforestation in 

 the regulation of ChihH floods is that by Air. H. Vander Veen, C. E.. 

 who has been for many years consulting engineer to the Natural Con- 

 servancy Bureau in Peking. At the conclusion of one of his recent 

 reports he wrote as follows : 



"I have dealt in the foregoing pages with the causes of the frequent floods in 

 the Chihli province and have endeavored to explain how the conditions can be 

 improved by providing a sufficient outlet for the flood water. But with that the 

 danger of floods has not been removed altogether, for there remains still the 

 difficult problem to settle what to do with the quantities of silt which the river 

 could not bring down to the sea, notwithstanding the improved outlet. 



"As long as the slope of the water level is such that a current can be main- 

 tained strong enough to carry all the matter held in suspension along, no harm is 

 done. But, as I explained in the beginning of this report, the natural slope of 

 the plain is, for several rivers, insufficient. In such a case the river is therefore 

 forced to get rid of the soil, held in suspension, along its way, consequently its 

 bed gets raised and in the long run the river has to find another course, which 

 it does by bursting its dikes to find in the lower lying land the place where it can 

 deposit its burden, which it could carry no longer and for which no more room 



