RIVER EMBANKMENTS. 
405 
are attended, too, with some collateral disadvantages. They 
deprive the earth of the fertilizing deposits of the waters, 
which are powerful natural restoratives of soils exhausted by 
cultivation; they accelerate the rapidity and transporting 
power of the current at high water by confining it to a nar¬ 
rower channel, and it consequently conveys to the sea the 
earthy matter it holds in suspension, and chokes up harbors 
with a deposit which it would otherwise have spread over a 
wide surface; they interfere with roads and the convenience 
of river navigation, and no amount of cost or care can secure 
them from occasional rupture, in case of which the rush of the 
waters through the breach is more destructive than the natural 
flow of the highest inundation.* 
as many circumstances concur to prove, the sinking of the plain near the 
coast may both tend to prevent the deposit of sediment in the river bed by 
increasing the velocity of its current, and compensate the elevation really 
produced by deposits, so that no sensible elevation would result, though 
much gravel and slime might be let fall. 
* To secure the city of Sacramento in California from the inundations 
to which it is subject, a dike or levee was built upon the bank of the river 
and raised to an elevation above that of the highest known floods, and it 
was connected, below the town, with grounds lying considerably above the 
river. On one occasion a breach in the dike occurred above the town at 
a very high stage of the flood. The water poured in behind it, and over¬ 
flowed the lower part of the city, which remained submerged for some 
time after the river had retired to it3 ordinary level, because the dike, 
which had been built to keep the water out, now kept it in. 
According to Arthur Young, on the lower Po, where the current of the 
river has been elevated much above the level of the adjacent fields by 
diking, the peasants in his time frequently endeavored to secure their 
grounds against threatened devastation through the bursting of the dikes, 
by crossing the river when the danger became imminent, and opening a 
cut in the opposite bank, thus saving their own property by flooding their 
neighbors’. He adds, that at high water the navigation of the river was 
absolutely interdicted, except to mail and passenger boats, and that the 
guards fired upon all others; the object of the prohibition being to prevent 
the peasants from resorting to this measure of self-defence .—Travels in 
Italy and Spain , Nov. 7, 1789. 
In a flood of the Po in 1839, a breach of the embankment took place at 
Bonizzo. The water poured through and inundated 116,000 acres, or 181 
