|
|
Topography |
 |
|
|
|
Bathymetry |
|
During
a survey in 1981, the bathymetry of the estuary was established.
The estuary was relatively shallow, with the deepest measurement
taken at 1km from the mouth, measuring 1,8m.
The water depth at the mouth was 0,6m at the time of the survey,
on 1 December 1981 (Ref. 1).
|
|
|
Obstructions |
|
In
1981, a high concrete bridge crossed the Eerste River 3km from the
mouth, carrying the road to the Macassar Sewage works, but this had
sufficient clearance for minimal obstruction of floodwaters. This bridge was beyond the observed limit of tidal
penetration. In 1981, a
small temporary wooden bridge crossed the estuary channel near the
observed tidal limit, 1,5km from the mouth.
As any major flood would carry this temporary crossing away it
was not considered to be an obstruction (Ref. 1).
|
|
|
Outcrops of rocks from the Malmesbury Group
near the sewage outfall in the channel are a natural obstruction and
collect driftwood (Ref. 1).
|
|
In 1981 a short section of the fence on the
west bank of the estuary, 900m from the mouth, at the boundary of the
then Kentron controlled area, had flood debris adhering to it indicating
some degree of obstruction (Ref.
1).
|
|
In 1981 the then Kentron boundary fence,
embankment and road causeway on the east side of the estuary were a
complete obstruction, totally isolating the wetland area, which was
formerly the eastern area of the Eerste River estuary.
|
|
The
Macassar Sewage Works has been constructed in part of the original
estuarine flood plain (Ref.
1).
|
|
|