“ The rate of advance at Fiumicino is estimated at 13 ft. per annum. From Rome to the sea the fall is only 6.5.: 1000. The arm which reaches the sea at Fiumicino is a canal, dug by Claudius and improved by Trajan (see Portus) , which partially silted up in the middle ages, and was reopened for navigation by Paul V. in 1612, 2 1/2 m. long, 80–130 ft. wide, and with a minimum depth of 5 ft. The lower course of the Tiber has been from the earliest ages subject to frequent and severe inundations ”

“ The total length of the river is 240 m., of which 21 m. lie between Rome and the sea. This latter portion of the river's course is tortuous, but in spite of this, and although the depth varies from only 7 to 20 ft., and in places at low water does not exceed 4 ft., it is nevertheless navigated by vessels up to 180 tons burden and proposals have been made to embank and dredge it so as to increase this depth to 8 ft. at least, or to build a ship canal up to Rome. The area of the Tiber basin is 6845 sq. ”

“ Still it has advanced at each mouth about 2 m. since Roman times, while the effect of the sediment it brings down is seen on the north-west almost as far as Palo (anc. Alsium) , and on the south-east beyond Tor Paterno (see Laurentina Via) in the gradual advance of the coast. ”