Catchment Modelling for Blackwattle Bay

49255 CATCHMENT MODELLING 1
49255 CATCHMENT MODELLING
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49255 CATCHMENT MODELLING 2
Catchment Details:
The catchment area of the Blackwattle bay is situated in Sydney ́s inner city suburbs.
This area covers 315 hectares and it also have other 50 hectares of land which drains directly into
Blackwattle Bay. The other section is draining to the Sydney water ́s chief stalk drainage system
which is employed to route flows from the upper section of this catchment. The reliability of this
flood relates to the topography nature in this area and also the capacity of service given by the
assets drainage. The catchment slope pattern is stepper in the upper area, it is steep and undulant
in the center section and also flat at the lower section which is closer to Blackwattle Bay.

49255 CATCHMENT MODELLING 3
Table of Contents
Catchment Details:......................................................................................................... 2
Table of Contents....................................................................................................... 3
Introduction:................................................................................................................... 4
Rainfall estimation (Generation).......................................................................................... 7
Runoff estimation............................................................................................................ 9
Initial losses................................................................................................................ 9
Depression storage and surface wetting...........................................................................9
Interception:........................................................................................................... 10
Continuing losses:....................................................................................................... 10
Evaporation:........................................................................................................... 10
Infiltration:............................................................................................................ 11
MODEL BUILD............................................................................................................ 11
Sewer Flow Modeling:................................................................................................. 11
Overland flow modelling:............................................................................................. 12
Hydraulic Modelling (Transport).................................................................................... 12
Bridges and Culverts................................................................................................ 12
Hydraulic Roughness................................................................................................ 13
Modelling of Flow Obstructions in the Floodplain............................................................13
Bibliography............................................................................................................. 16

49255 CATCHMENT MODELLING 4
Introduction:
For this project we are checking on the impact of the pluvial and fluvial flows in the
catchment areas which are draining into Blackwattle bay. There are two basic issues which
needs to be considered during the conceptual modelling and this modelling should be done in
regards to two scenarios (Kleinman, 2015). Pluvial is a type of flooding that is more linked to its
cause being rainfall. In most cases it occurs due to heavy rainfall, these heavy downpour results
to surface water runoff whose capacity is more than that of the city ́s drainage system. It is very
hard to foretell pluvial than other flooding types like fluvial since it occurs in a short span of time
duration and it can also pond before it is a runoff (Blanc, 2012).Basically pluvial flooding
correlates to direct ponding or runoff before going into a system of drainage.
For this project we can use the two phenomena that is watercourse flooding, runoff and
also surcharge which can be employed as pluvial flooding components (Feyen, 2012). All these
three can be connected together and then they are modelled in pluvial flooding section. A part
from the aforementioned three we can as well consider the groundwater such as the fluvial
flooding (Apel, 2016). As aforementioned pluvial flooding due to prolonged rainfall which can
fall in areas like gardens, impervious regions like footpaths and streets which is illustrated in the
diagram below which was taken from one of the streets in Blackwattle Bay;