Catchment Modeling Task Case study 2022

CATCHMENT MODELLING TASK
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Catchment Details
Blackwattle Bay catchment area is situated in the central region of Sydney and enclosed by
Ultimo, Camper down, Forest Lodge, Darlington, and Glebe among others as demonstrated in
the figure below. The area has undergone extensive development where land is in most cases
used for the purposes of high-density and high-rise residential, commercial as well as industrial
buildings and facilities. Consequently, green and open spaces for instance Wentworth Park tends
to be limited within the catchment area. The coverage of the catchment area is about 315
hectares in total area where to the tune of almost 50 hectares get discharged into the sea directly.
Other regions get directly discharged into the main drainage system of Sydney by Branch
drainage system
Figure 1: Blackwattle Bay catchment area

Introduction
The purpose of this task is to come up with the design of a catchment modelling system for the
assessment of the effects of fluvial as well as pluvial flood on catchments that flow into the
Blackwattle Bay of Sydney. Hence the main objectives of the research of the catchment
modeling are pluvial and fluvial flood. Simultaneously, the conceptual model should be design
for the mentioned two challenges.
Fluvial floods are as a result of rise in the levels of water in the waterways or rivers. Suppose the
rain goes beyond the cumulative capacity of a river after a heavy rain, it often results in risk of
the river bank break off and fluvial flooding. In such a case, the water would be observed to spill
over to the neighbouring commercial as well as residential regions; One of the major factors of
fluvial flooding revolves around the condition of rainfall for instance the intensity of the rainfall
the distribution as well as the time (Bermúdez et al., 2017). Another yet important factor is the
soil conditions for example the soil humidity, impervious regions distribution as well as the
amount of vegetation among other factors on soil. Fluvial floods may be pre-fetched in any case.
Suppose it rains or the icebergs melt, it takes some quality time to collect and can thereafter
result in formation of floods. During such a period the rise in the levels of water may go on for
days or even weeks and people may foresee flood risks and put in place the required measures
through observation of the variations in the levels of water.
Pluvial floods are as a result of prolonged or heavy rainfall. The major reason is that the runoff
as result of rainfall goes beyond the amount of load that the urban drainage systems is able to
sufficiently sustain as well as that which may be sustained by the natural drainage systems that
are available. In such a case, the city would form conditions in which there is accumulation of
water. The submerged regions may drain the water slowly through the available drainage

systems (Dadson et al., 2017). In suburbs or regions that have grass growing over them and do
not have drainage systems, such waters may just be removed through evaporation otherwise they
will remain in the region for a long time. Among the factors responsible for pluvial flooding
include:
 Rainfall situation for instance rainfall intensity
 Geological environment inclusive of the soil humidity, condition of the existing
vegetation, distribution level of the impervious regions as well as the terrain height
 capacity of the available sewer machines and equipment for instance the drainage
capacity of pipeline as well as working conditions of the facilities of the pipeline
The floods that commonly occur in cities are pluvial floods which in most cases tend to be quite
challenging to prevent since pluvial floods bear features of high intensity as well as short periods
of time (Griffiths et al., 2019). With regard to this assignment, it would thus be majorly dwelling
on the case of pluvial floods thus the report will demonstrated the four major conceptual
components among them generation, collection, disposal as well as transport for the design of an
efficient and effective modeling system in the chapter that follows
Estimation of Rainfall (Generation)
Rainfall is an integral aspect of the generation component. The approximation of rainfall has a
direct effect on the model type as well as the level of accuracy of the prediction. The significant
factors are at play when it comes to estimation of rainfall and such include rainfall duration,
rainfall intensity as well as the extent or degree of rainfall. Pluvial flooding disasters normally
take place in rainfall of high intensity and small spatial scale that is below 10km. The size as
well as spatial distribution of pluvial flooding is as well hard to detect and predict. Blackwattle