As a proper noun riverside
is a place name applied to a locality, especially a city, that is situated beside a river.
As a noun riverbed is
the path where a river runs, or where a river once ran; the bottom earthen part of a river, not including the riverbanks.
riverside
English
Noun
A bank or side of a river.
* Gonna lay down my burden; Down by the riverside ...
Adjective
(-)
At or near the side of a river.
riverbed
English
Alternative forms
* river bed
Noun
(
en noun)
The path where a river runs, or where a river once ran; the bottom earthen part of a river, not including the riverbanks.