Brisbane Water Plan of Management - Gosford City Council - NSW ...

6.0 WATER DEPTH AND SEDIMENTATION
Rates of sedimentation within Brisbane Water and local water depths were analysed as part of
this plan by the Coast and Estuaries Directorate of the Department of Land and Water
Conservation by comparing hydrographic data between 1901 and 1992. The study area
covered the main waterways of Brisbane Water except the Woy Woy Bay or Bays area and
Phegans Bay because they were isolated from the main water body by a rail line causeway.
Table 4 and Figures 20 to 22 outline the geological elements and cross-section data of Brisbane
Water which indicated the general direction of the vertical change as erosion, accretion, or in
some cases both processes occurring. Taking into account the results of the hydrographic
analysis it appears that there is recent sedimentation occurring at the outlets of drains and creek
systems entering Brisbane Water, however no identifiable trends suggest that Brisbane Water is
steadily accreting material or being eroded to any degree of concern. On the whole, the extent
of the estuary appears to be stable.
The plan recognises the need to minimise any further erosion within the catchment of Brisbane
Water and sedimentation within and around Brisbane Water itself. Accordingly, monitoring of
creek and major drainage outlets is considered warranted to investigate sediment and nutrient
control methods by Council to reduce and prevent any degradation occurring to the waterway.
6.1 Management Objectives
Water Depth and Sedimentation
MANAGEMENT OBJECTIVES
PRIORITY
FOR
ACTION
RESPONSIBILITY
a
Determine siltation rates by checking general water depths
with historic chart information.
H
Council,
LAWC (C&E),
LAWC (SCS)
b
Determine the original, age, nutrient content and existing
pollutants by sediment sampling.
H
Council,
LAWC (C&E), LAWC
(SCS)
c
Identify the need for further sedimentation studies for
Brisbane Water.
H
Council,
LAWC (C&E), LAWC
(SCS)
d
To correct existing and minimise further sedimentation
occurring within and around Brisbane Water.
H
Council,
LAWC (C&E), LAWC
(SCS)
6.2 Management Guidelines
Water Depth and Sedimentation
MANAGEMENT GUIDELINES
PRIORITY
FOR
ACTION
RESPONSIBILITY
a
Council continue to enforce its Erosion and Sedimentation
Control Policy to minimise and avoid the generation of any
soil erosion within the catchment and around the foreshore
areas of Brisbane Water.
H
Council,
LAWC (SCS)
Brisbane Water Plan of Management - July 1995 Page 26