The worsening situation was exacerbated by the steady draining of artesian water from the bedrock underneath the lagoon to satisfy the heavy demands of local industry, which led to the progressive sinking of the terrain of Venice. After an aqueduct from the mountains was installed in the early 1970s to provide an alternative water supply for the industrial complex at Porta Marghera, the rate of subsidence was reduced, but serious damage had already been done. The disastrous flood in Florence in 1966 was almost as severe in Venice, yet attracted relatively little notice abroad. In 1969, however, a unesco report on the physical condition of the city raised 173 Palazzo del Casino, Lido, by Miozzi and Quagliata, begun 1936 international alarm by predicting the almost total decay of the stonework within a few decades. Luckily this ominous warning proved exaggerated, but it had the welcome effect of rousing international bodies to become involved in the preservation of the city. The architectural heritage of the city was suffering from similar ills to those that were gradually driving away the inhabitants. Repeated flooding, corrosion caused by atmospheric pollution, and erosion by waves stirred up by motor boats, constantly threatened the survival of ancient buildings. The worst wave damage occurred in the narrower canals, such as the Rio di Ca’ Foscari where the motor traffic was particularly heavy. In 1938 an extension to this rio, a newly excavated channel called the Rio Nuovo, had been opened to provide an express route for motor boats between Piazzale Roma and the centro storico 44 And as the motor-boat traffic grew, so the survival of the gondola was seriously threatened.