Narellan Creek Overland Flood Study (Vol 1) - Flipbook - Page 26
Narellan Creek Catchment
Flood Study
Most of the above layers served as a basis for preparing the various figures displaying the
study results (most notably the aerial photography and cadastre). In this regard, the layers
were fit for purpose.
However, the stormwater information served as a key input in the updated hydraulic model
for the study. As a result, these layers were reviewed in detail and the outcome of this
review is provided below.
As part of this review, it was noted that the stormwater GIS layers provided by Council did
not cover the full extent of the stormwater system. Therefore, it was also necessary to draw
upon the stormwater information contained within the TUFLOW hydraulic model discussed
in Section 2.2.4. The outcomes of the review of the TUFLOW stormwater layers are also
presented below.
2.5.1
Stormwater
Design Plans
Camden Council extracted stormwater pit and pipe details from a range of design plans.
The GIS layers focused on new areas that have been developed since the preparation of the
8Update of Narellan Creek Flood Study9 (PWA, 2017). The extent of the stormwater GIS
information extracted from the design plans are shown in Figure 2.
A review of these GIS layers determined that they contained details of 6,441 pipes and
6,491 pits. Attached to each pit and pipe were a range of attributes, including:
Pipes:
•
Size
•
Length
•
Upstream invert elevation
• Downstream invert elevation
Pits:
•
Pits type (including lintel lengths)
•
Sag versus on grade
•
Invert elevation
Overall, the supplied attributes were sufficient to fully define these sections of the
stormwater system in the hydraulic model.
However, some limitations were identified with the stormwater GIS layers, including:
Pipes:
•
Adverse/reverse pipes slopes: 33 occurrences
•
Pipe invert located below pit invert: 49 occurrences
• Isolated pipe (i.e., pipe not connected to pits): 56 occurrences
Pits:
•
Isolated pits: 221 occurrences
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