EM 1110-2-1100 (Part I)
30 Apr 02
I-3-3. Roman Times
The Romans introduced many revolutionary innovations in harbor design. They learned to build walls
underwater and constructed solid breakwaters to protect exposed harbors. They used metal joints and clamps
to fasten neighboring blocks together and are often credited with discovering hydraulic cement made with
pozzolanic ash obtained from the volcanic region near Naples, which hardens underwater. Frost (1963) notes
that the Greeks had used hydraulic cement long before the Romans. The Romans replaced many of the Greek
rubble mound breakwaters with vertical and composite concrete walls. These monolithic coastal structures
could be built rapidly and required little maintenance. In some cases wave reflection may have been used
to prevent silting. In most cases, rubble or large stone slabs were placed in front of the walls to protect
against toe scour. The Romans developed cranes and pile drivers and used them extensively in their
construction. This technology also led them to develop dredges. Another advanced technique used for deep-
water applications was the watertight floating cellular caisson, precursor of the modern day monolithic
breakwater. They also used low, water-surface breakwaters to trip the waves before they reached the main
breakwater. The peculiar feature of the vertical wall breakwater at Thapsus (Rass Dimas, Tunisia) was the
presence of vents through the wall to reduce wave impact forces. This idea is used today in the construction
of perforated caisson breakwaters (Franco 1996).
Using some of these techniques, the Romans built sophisticated breakwaters at Aquileia, Italy (ca. 180 B.C.),
and at Caesarea, Israel (ca. 20 B.C.). The southwestern breakwater at Caesarea contained a "forebreakwater"
that acted as a submerged reef that "trips" the wave causing it to break and dissipate energy before
encountering the main breakwater (Inman 2001).
The largest manmade harbor complex was the imperial port of Rome; the maritime town at the mouth of the
Tiber River was named Portus (The Port). It is now some four km from the sea, partly buried under Rome-
Fiumicino airport. Despite its importance to the capital of the empire, (300,000 tons/year of wheat from
Egypt and France), the harbor always suffered siltation from the river. Trajan, who also built the ports of
Terracina and Centumcellae, built Portus' inner hexagonal basin. The port of Centumcellae was built just
to serve his villa at a site with favorable rocky morphology. A grandiose engineering project between 107-
106 B.C. created a sheltered bathing and boating retreat. Slaves from all parts of the empire excavated a
harbor and hauled in massive stones to create an artificial harbor to dampen the force of the waves. After the
decline of Portus, it became, and remains, the Port of Rome. After remaining unchanged for over 1,000 years,
the inner Roman Basin, which was dredged from rock (200,000 m3 or 260,000 yd3), is still in use. Roman
engineers also constructed harbors in northern Europe along the main waterways of the Rhine and Danube
and in Lake Geneva. They became the first dredgers in the Netherlands to maintain the harbor at Velsen.
Silting problems here were solved when the previously sealed solid piers were replaced with new "open"-
piled jetties. In general, the Romans spread their technology throughout the western world. Their harbors
became independent infrastructures, with their own buildings and storage sheds as opposed to the pre-Roman
fortified city-enclosed harbors. They developed and properly used a variety of design concepts and
construction techniques at different coastal cites to suit the local hydraulic and morphological conditions and
available materials (Franco 1996).
The Romans also introduced to the world the concept of the holiday at the coast. The ingredients for beach
holidays were in place: high population density coupled with a relatively high standard of living, a well-
established economic and social elite, and a superb infrastructure of roads. From the end of the republic to
the middle of the second century of the empire, resorts thrived along the shores of Latium and Capania, and
an unbroken string of villas extended along the coast from the seashore near Rome to the white cliffs of
Terracina. Fine roads connected these resorts to the capital, allowing both the upper crust and the masses to
descend from sultry and vapor-ridden Rome to the sea. For five hundred years, the sybaritic town of Baiae
reigned as the greatest fashionable beach resort of the ancient world. Seneca the Younger called Baiae a
History of Coastal Engineering
I-3-3
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