An initial parameter estimation approach for urban catchment modelling

Figures & data

Figure 1. Location and remote sensing image of Alexandria Canal catchment.

Figure 2. Subcatchment delineation and outlet.

Table 1. Catchment data.

Name	Type	Source	Pre-processing
Remote Sensing Image	RGB Image	NSW Spatial Service	Labelling, Clipping small images (256x256) for the training set
Subcatchments Map	GIS Shapefile	City of Sydney Council	Combine some subcatchments that belong to the same drainage subsystem or depression. There are 1534 subcatchment after merging.
Stormwater Drainage Map	GIS Shapefile	City of Sydney Council	The stormwater pits of one subcatchment with the lowest invert level will be chosen as the subcatchment outlet. Only one outlet was assigned to each subcatchment.

Figure 3. Methodology framework.

Figure 4. Structure of U-Net.

Figure 5. Schematic of idealised catchment shape to show the relationship between catchment width and flow lengths. W is subcatchment width, L is flow length.

Figure 6. Alexandra Canal catchment raw image and LULC prediction.

Table 2. Confusion matrix of prediction.

Classname	Tree	Water Body	Pervious	Impervious	Total	U_Accuracy
Tree	56	0	7	2	65	0.8615
Water Body	2	8	0	0	10	0.8000
Pervious	7	1	66	3	77	0.8571
Impervious	7	0	24	323	354	0.9124
Total	72	9	97	328	506
P_Accuracy	0.7778	0.8889	0.6804	0.9847

P_Accuracy = Prediction Accuracy

U_Accuracy = User Accuracy

Overall Accuracy = 0.8953

Kappa = 0.7900

Figure 7. Subcatchments imperviousness fraction distribution histogram.

Figure 8. Subcatchments impervious fraction accumulated likelihood curve.

Figure 9. (a) Subcatchments’ conceptual flow length distribution and (b) accumulated likelihood curves of conceptual flow length (1534 subcatchments).

Table 3. KS test and p-values.

	All LULC/Impervious	All LULC/Pervious	Impervious/Pervious
KS statistic	0.0156	0.0613	0.0535
p-value	0.9918	0.0062	0.0248

Figure 10. Accumulated likelihood distribution of CFL/Std width ratio.

Data availability statement

Raw data were generated at Spatial Service NSW and City of Sydney Council. Derived data supporting the findings of this study are available from the corresponding author SG on request.