Mr. Todd. 
342 DISCUSSION: FORESTS, RESERVOIRS, AND STREAM FLOW 
In connection with a drainage project in the Mississippi Delta, in 
attempting to ascertain the proper percentage of run-off to rainfall, the 
writer was surprised to discover, from a very carefully compiled table 
of run-off compared with rainfall, covering the entire Mississippi 
Valley, that seemingly the flatter the slope the greater the percentage 
of run-off. The table referred to is contained in a publication by the 
Weather Bureau,* from which the following extract is taken: 
“Normal Annual Discharge from River Basins.” 
‘* Ratio of 
“ Basin. discharge to 
downfall. 
“OHIO sakes 66 ane cee Peewee EES Pe ote eae 0.300 
Upper Mississippi ....... 02. e ee eee cence eee cee eee 0.275 
DM SSOUTE. rec sare ho oe ea ee ke BGS oe etree 0.150 
ArKanSa8  e ccdacesie ose e a Wee wee wie ere a qari anes HOSES 0.156 
Redo sc cies be can bares RASA wees AOS Re eee sais keeles 0.220 
Central “ Valléyacaxdeve uses eed Gav dec ewan 0.515.” 
Commenting on this table, in the same publication is found the 
following: 
“The Central Valley includes about 30000 square miles of swamp 
land and 39000 square miles of upland; the ratio over the former is 
doubtless much greater and over the latter much less than this 
average.” 
It is a noteworthy fact that even at this date probably less than 
40% of the swamp area of the Central Valley is deforested, and where 
the timber has been cut, vegetable growth is very rank and luxuri- 
ous, and conditions would seem to be in every way ideal for the con- 
servation of the rainfall. 
In regard to the caving banks on the Lower Mississippi, Colonel 
Chittenden is correct in his statement: “The problem is strictly 
a local one, and the remedy must be a local one.” 
It is a fact that neither extreme high nor low waters are very greatly 
to be feared as causing excessive caving; in fact it has been the writer’s 
observation, checked by actual surveys and measurements, that the 
greatest amount of caving is usually coincident with periods when 
moderately high stages occur in succession, alternating with a drop to 
about a three-quarter bank-full stage. Of course, no general rule 
can be stated as applicable to caving banks, but in the main the fore- 
going conditions produce acute caving in the bends, where nearly 
always important levee locations and valuable plantation improve- 
ments are destroyed. Hence reforestation, no matter how generally 
accomplished, could not hope to cure this very distressing and acute 
problem of river improvement. The same conclusion is equally ap- 
plicable to any effect proposed reservoir systems might have on the 
stages of the river. As to local forests checking caving banks, it has 
** Floods of the Mississippi River,” Bulletin E, 1897, p. 27. 
