DRAINAGE OF WET LANDS OF SOUTHERN LOUISIANA. 69 



Rainfall, water pumped, and reservoir stages due to heaviest storms, etc. — Con. 



Date. 



Rain- 

 fall. 



Water 

 pump- 

 ed. 



Stage of water in 



reservoir above 



(+) or below (— ) 



No. of 

 hours 

 land 

 flood- 

 ed. 



Condition of soil before storm. 







general surface. 







Inches. 



Inches. 



8 a. m. 



8 p. m. 







1911. 



Feet. 



Feet. 





Apr. 25 



1.02 



.00 



-2.0 



-1.8 



I 





26 



27 



2.02 

 .00 



.56 

 .83 



—1.6 

 -0.5 



—1.2 

 -2.8 



° 



Well drained, and three-fourths in cultivation. 



28 



.22 



.23 



-1.8 



-3.5 



1 





Nov. 27 



3.00 



.47 



-0.3 



-0.2 



I 





28 



.00 



.88 



-0.6 



-3.0 



f ° 



Do. 



29 



.00 



.34 



-0.3 



-2.0 



1 





1912. 















May 1 



.30 



.00 



. -3.3 



-3.0 







2 



.00 



.00 



-2.8 



-2.7 







3 



.41 



.00 



-2.6 



-2.5 







4 



.00 



.00 



-2.4 



-2.3 







5 



1.05 



.00 



-2.1 



-1.6 







Well drained, and seven-eighths in cultivation. 



6 



1.21 



.55 



-1.4 



-0.6 







7 



.00 



.68 



-0.5 



-0.6 







8 



.00 



.56 



-1.6 



-2.6 







9 



.00 



.11 



-2.6 



-1.5 







From an examination of the above table it will be seen that it was only 

 during four of these storms that flooding occurred. It is also apparent that if 

 the plant had been operated at full capacity flooding would not have occurred 

 during any of the storms. The flooding was due to unreliable machinery 

 rather than to insufficient theoretical capacity; during the storms of Septem- 

 ber and December, 1909, the plant was operated at less than half its maximum 

 capacity. In determining the proper capacity of plant to remove these heavy 

 storms it will be necessary to consider only those of August, 1909, and July, 

 1910. The flooding that occurred on this tract due to these two storms was on 

 only a relatively small portion in the immediate vicinity of the reservoir, and 

 in neither case did it damage crops, as the water was only about 4 inches deep 

 on the ground. In the storm of August, 1909, a pumping capacity of 0.85 inch 

 would have been sufficient to prevent damaging overflow. The total water 

 removed was 2.90 inches. By starting the pumps on August 9, or one day 

 earlier than was done, a capacity of about 0.75 inch would have served to take 

 away all drainage water in time to prevent flooding, as the water would all 

 have been removed more than 24 hours sooner than actually occurred. In the 

 storm of July, 1910, by starting a plant of a capacity of 0.75 inch on July 2 

 the run-off of the 2d and 3d could have been taken out on the 2d, thus 

 making a gain of 24 hours. It is not possible to estimate exactly the effect of 

 such a gain, but it would appear that the time of flooding would have been 

 reduced to about 12 hours. By applying a pumping capacity of 0.75 inch per 

 day to the other storm periods it will be seen that the run-off could all have 

 been removed without flooding, although the reservoir probably would have 

 stood nearly full for some days. This condition would be allowable two or 

 three times a year without damage to crops. After a period of cultivation of 

 several years the soil on this tract will become more impervious and the 

 intensity of run-off will be greater. 



