Wikipedia
Vadathodu
Vadathodu is a small stream in North Paravur flowing towards the Periyar river, which was once used as an International boundary separating the Kingdom of Cochin from the Travancore Kingdom. On its west lay Travancore ( Madaplathuruthu and Moothakunnam), and on its east was Kingdom of Cochin ( Vadakkumpuram and, of course, Chendamangalam where Paliath Achan, the Cochin Kingdom's minister lived).
There is one story about this boundary. One thief was chased by the police of one kingdom, crossed the Vadathodu over to the other kingdom, and he escaped, as the police had to simply watch on helplessly.
One bridge was built over Vadathodu on 11 November 1955 to connect both Vadakkumpuram and Madaplathuruthu.