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Table 1

Results of WSC Toolkit simulation on stormwater management benefits

Benefit	Indicators	No treatment	Lined Bioretention	Lined Bioretention + harvesting	Unlined Bioretention	Wetland	Pond	Ideal values
Treatment performance	Volume reduction (%)^a	0	7	43	16	26	27	–
	TSS reduction (%)	0	93	96	93	71	78	85^b
	TP reduction (%)	0	71	82	73	66	67	45^b
	TN reduction (%)	0	68	80	70	52	45	45^b
Water captured	Water supplied (ML/year)	0	0	3.2	0	0	0	–
Stream hydrology and water quality	Number of runoff days per year	97	136	106	322	355	355	–
	Proportion of runoff volume reduction (%)	0	5.6	34.6	5.6	6.7	5.3	–
	Proportion of filtered volume (%)	0	0.1	0.1	0.0	0.0	0.0	78/93^c
	Water Quality – TSS (mg/L)	201.5	2.6	2.3	2.4	6.0	12.1	20^d
	Water Quality – TP (mg/L)	0.41	0.11	0.11	0.11	0.06	0.09	0.05^d
	Water Quality – TN (mg/L)	2.86	0.6	0.6	0.6	1.1	1.4	0.60^d
Stream erosion and minor flooding	3 month ARI peak flow reduction	0	38	63	38	64	70	–
	2 year ARI peak flow reduction	0	20	30	20	32	44	–
	Stream Erosion Index (SEI)	4.1	2.1	1.4	2.0	1.2	0.8	2/1^e

Benefit	Indicators	No treatment	Lined Bioretention	Lined Bioretention + harvesting	Unlined Bioretention	Wetland	Pond	Ideal values
Treatment performance	Volume reduction (%)^a	0	7	43	16	26	27	–
	TSS reduction (%)	0	93	96	93	71	78	85^b
	TP reduction (%)	0	71	82	73	66	67	45^b
	TN reduction (%)	0	68	80	70	52	45	45^b
Water captured	Water supplied (ML/year)	0	0	3.2	0	0	0	–
Stream hydrology and water quality	Number of runoff days per year	97	136	106	322	355	355	–
	Proportion of runoff volume reduction (%)	0	5.6	34.6	5.6	6.7	5.3	–
	Proportion of filtered volume (%)	0	0.1	0.1	0.0	0.0	0.0	78/93^c
	Water Quality – TSS (mg/L)	201.5	2.6	2.3	2.4	6.0	12.1	20^d
	Water Quality – TP (mg/L)	0.41	0.11	0.11	0.11	0.06	0.09	0.05^d
	Water Quality – TN (mg/L)	2.86	0.6	0.6	0.6	1.1	1.4	0.60^d
Stream erosion and minor flooding	3 month ARI peak flow reduction	0	38	63	38	64	70	–
	2 year ARI peak flow reduction	0	20	30	20	32	44	–
	Stream Erosion Index (SEI)	4.1	2.1	1.4	2.0	1.2	0.8	2/1^e

^aFor the Volume reduction in the Treatment Performance, it only applies to the treatment system (considering in and out), meanwhile exfiltration loss is considered.

^bFrom BPEM (VSC 1999).

^c78 – catchment with pasture vegetation and 93 – catchment with forest vegetation: these were derived according to the model by Zhang et al. (2001).

^dvalues suggested by Walsh et al. (2012) for stream health.

^eBrookes & Wong (2009) suggested that the ‘best practice’ SEI that should be achieved is 2 with a stretch target of 1.

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