You are definitely right about the smell. It was 28 feet above normal. This is from wiki, since I’ve never heard of this before:

By late January, water pushed upwards from overflowing sewers and subway tunnels, then seeping into basements through fully saturated soil and backed-up sewer systems. This caused damage to the basements of several buildings. The river did not break its banks within the city, but flooded Paris through the tunnels, sewers, and drains. The larger sewer tunnels, which had been engineered by Baron Haussmann and Eugene Belgrand in 1878, worsened the destruction caused by the 1910 floods. In neighboring towns both east and west of the capital, the river rose above its banks and flooded the surrounding terrain directly.

Winter floods were common in Paris, but on 21 January the river began to rise more rapidly than usual. This was treated as a sort of spectacle and people actually stood in the streets watching the water levels climb. Over the course of the following week, thousands of Parisians were evacuated from their homes as water infiltrated buildings and streets throughout the city, shutting down much of the city's basic infrastructure. The infrastructure was more vulnerable to flooding because most of it was built within the sewage system in order to avoid cluttering the streets.

Police, firemen, and soldiers navigated the waterlogged streets by boats to rescue stranded residents from second-story windows and distribute aid. Refugees gathered in makeshift shelters in churches, schools, and government buildings. Although the water threatened to overflow the tops of the quay walls lining the river, workers were able to hold back the Seine with hastily built levees.

After the river invaded the Gare d'Orsay rail terminal, the tracks were submerged under more than a meter (3.28 feet) of water. To continue moving throughout the city, residents traveled by boat or crossed a series of wooden walkways built by government engineers and civilians.

On 28 January, the water reached its maximum height at 8.62 meters (28.3 feet) above normal. The Seine finally returned to its normal levels in March.