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ROOIELS RIVER ESTUARY: Physical Features |
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Topography |
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The river has a steep gradient, is shallow and is very narrow in its upper catchment area. It is consequently fast flowing with many small rapids and waterfalls. There are no known data available for volumetric flow. (Ref 1) |
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The estuary which is flanked by the steep slopes of the Kogelberg mountains has a multi-channel configuration through its floodplain, with the main water body above the road being roughly H-shaped. The river course was displaced seawards with the building of the coastal road. The river now enters the beach area under the road bridge on the northern side of the floodplain, and then swings southward running parallel to the road before turning west to enter the sea alongside a rocky point at the western extremity of the bay. (Ref 1) |
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Bathymetry |
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The estuary is generally less than 1 m deep; however, the main channel under the bridge had been scoured to a depth of 3,0 m at the time of the ECRU survey in December 1979. When the mouth is open the depth increases slightly at high tides with the seawater pushing up into the estuary. (Ref 1) |
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Obstructions |
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Catchment: There are no artificial obstructions but, as mentioned above, numerous small rapids and waterfalls are present in the upper catchment area. (Ref 1) |
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Near the mouth: Aerial photographs taken during 1938 show that at the time the river formed an extensive meander across the lower end of its floodplain. It is evident that with the construction of the bridge and embankment for the coastal road in the early 1950's, the main flow channel was relocated towards the northern side of the floodplain under the present road bridge and the river established a meander on the seaward side of the road embankment so as to enter the sea at its former position. Wooden pylons of an old bridge can be seen in the southern arm of the estuary above the road. The uniform width and shape of the channel connecting the northern and southern arms of the upper estuary suggests that this channel was artificially formed when the new bridge was built. (Ref 1) |
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