Most of us think of the Potomac as a rather benign river. As we can observe, it isn't always so.

Sometimes it goes on rampages, as it is doing now. And most capital longtimers, including those who experienced the backlash of Hurricane Agnes in 1972, are likely to recall the flood of 1936.

The picture with this story was taken from the Virginia shore of old Chain Bridge -- the seventh of eight spans on the site -- in March 1936. The bridge held, but was closed as the result of flood damage. It was rebuilt and reopened in 1939.

The late Washington Post reporter Edward T. Folliard reported that the 1936 flood gave the D.C. police department the first test of two-way radios to dispatch crews.

In March 1937, another flood hit, and President Franklin D. Roosevelt delayed a Florida holiday and bundled up to ride a touring car out to Chain Bridge to view the turbulent Potomac lapping the bridge deck.

Washington's worst flood damage came, historians note, on June 2, 1889, when the Potomac rose from the same storm that caused the tragic flood in Johnstown, Pa. Water several feet deep covered what is now the west Mall and the Federal Triangle. One can still see the high-water mark chiseled on an old sandstone ornamental post at 15th Street and Constitution Avenue NW.

According to D.C. Library records, on June 30, 1842, a torrential rainstorm formed a lake from the foot of Capitol Hill to the present site of the National Gallery of Art. In 1870, Long Bridge, the forerunner of the 14th Street bridges, was washed away, halting all railroad service to the south.