192 
Ohio Biological Survey 
Such banks as these are not depositional. They are found only along 
eroding parts of a river’s course. These herbaceous plants, which present 
no obstruction to flood waters, retain their foothold, even when the willows 
of the same association, or the trees higher up, are torn out. 
Steep river banks are found at or near the foot of b’ufifs. They are 
always narrow and often short-lived, as a flat beach-like shore may be 
built out in front of them. 
Under-cut banks .—All the streams except the Ohio are under-cutting 
their flood plains. These under-cut banks are comparable to bluffs in 
steepness, but they belong essentially to the flood plain area. Whatever 
vegetation may appear upon them during one year is swept away the next 
spring. It is only after under-cutting ceases, and the slopes become more 
gentle, that the flood plain vegetation gets a foothold. 
The plant associations of these steep river banks in silt or sand re¬ 
semble most closely those of the gently sloping shores in the same mate¬ 
rial. On the narrow flat at the base of such banks are the hydrophytic 
herbs of the broader shores. Above this are the other associations of 
gently sloping banks. These are often so intermingled that they can not 
be separated into zones (fig. 44). In other places the zones are very nar¬ 
row and at times one or more are eliminated entirely. 
P>. ISLANDS 
The islands of the Miami and Little Miami rivers are residual—rem¬ 
nants of a former valley Ailing, partially reworked, but produced by ero¬ 
sive rather than by depositional forces. They vary in size from a few hun¬ 
dred to several thousand feet in length. It is only the smaller ones which 
can properly be called islands. The larger ones are areas of the flood 
plain separated from the mainland by cut-offs (sloughs). They can be 
considered as islands only in that they are bounded on all sides by parts 
of the river and that their origin is the same as that of the smaller islands. 
It is the smaller islands which will be considered here. 
All gradations between the island and the cobble shore are found. 
Many projecting stretches of beach-like shore are separated from the 
higher flood plain by a depression, which during the summer is either 
swampy or partly filled with water (fg. 4/). Some stretches of shore 
connected with the mainland in but one or two places become islands dur¬ 
ing high water. The islands may be well in the center of the river so that 
the waters divide nearly equally in passing them (fg. 42), or so much to 
one side that the river is very unequally divided. Sometimes the shallow 
