he dock was located away from the main current to avoid deposition of silt. Modern oceanographers have observed that the Harappans must have possessed great knowledge relating to tides in order to build such a dock on the ever-shifting course of the Sabarmati, as well as exemplary hydrography and maritime engineering. This was the earliest known dock found in the world, equipped to berth and service ships.[33] It is speculated that Lothal engineers studied tidal movements, and their effects on brick-built structures, since the walls are of kiln-burnt bricks. This knowledge also enabled them to select Lothal's location in the first place, as the Gulf of Khambhat has the highest tidal amplitude and ships can be sluiced through flow tides in the river estuary. The engineers built a trapezoidal structure, with north-south arms of average 21.8 metres (71.5 ft), and east-west arms of 37 metres (121 ft).[34] Another assessment is that the basin could have served as an irrigation tank, for the estimated original dimensions of the "dock" are not large enough, by modern standards, to house ships and conduct much traffic.[3]
The original height of the embankments was 4.26 metres (13.98 ft). (Now it is 3.35 metres (10.99 ft).) The main inlet is 12.8 metres (42.0 ft) wide, and another is provided on the opposite side. To counter the thrust of water, offsets were provided on the outer wall faces. When the river changed its course in 2000 BCE, a smaller inlet, 7 metres (23 ft) wide was made in the longer arm, connected to the river by a 2 kilometre (3.2 mi) channel. At high tide a flow of 2.1–2.4 metres (6.9–7.9 ft) of water would have allowed ships to enter. Provision was made for the escape of excess water through the outlet channel, 96.5 metres (317 ft) wide and 1.7 metres (5.6 ft) high in the southern arm. The dock also possessed a lock-gate system—a wooden door could be lowered at the mouth of the outlet to retain a minimum column of water in the basin so as to ensure floatation at low tides.[34] Central to the city's economy, the warehouse was originally built on sixty-four cubical blocks, 3.6 metres (11.8 ft) square, with 1.2-metre (3.9-ft) passages, and based on a 3.5-metre-high (11.5 ft) mud-brick podium. The pedestal was very high to provide maximum protection from floods. Brick-paved passages between blocks served as vents, and a direct ramp led to the dock to facilitate loading. The warehouse was located close to the acropolis, to allow tight supervision by ruling authorities. Despite elaborate precautions, the major floods that brought the city's decline destroyed all but twelve blocks, which became the make-shift storehouse.
The original height of the embankments was 4.26 metres (13.98 ft). (Now it is 3.35 metres (10.99 ft).) The main inlet is 12.8 metres (42.0 ft) wide, and another is provided on the opposite side. To counter the thrust of water, offsets were provided on the outer wall faces. When the river changed its course in 2000 BCE, a smaller inlet, 7 metres (23 ft) wide was made in the longer arm, connected to the river by a 2 kilometre (3.2 mi) channel. At high tide a flow of 2.1–2.4 metres (6.9–7.9 ft) of water would have allowed ships to enter. Provision was made for the escape of excess water through the outlet channel, 96.5 metres (317 ft) wide and 1.7 metres (5.6 ft) high in the southern arm. The dock also possessed a lock-gate system—a wooden door could be lowered at the mouth of the outlet to retain a minimum column of water in the basin so as to ensure floatation at low tides.[34] Central to the city's economy, the warehouse was originally built on sixty-four cubical blocks, 3.6 metres (11.8 ft) square, with 1.2-metre (3.9-ft) passages, and based on a 3.5-metre-high (11.5 ft) mud-brick podium. The pedestal was very high to provide maximum protection from floods. Brick-paved passages between blocks served as vents, and a direct ramp led to the dock to facilitate loading. The warehouse was located close to the acropolis, to allow tight supervision by ruling authorities. Despite elaborate precautions, the major floods that brought the city's decline destroyed all but twelve blocks, which became the make-shift storehouse.
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