❓ The parliamentary question raises concerns about the effectiveness of drainage and water management strategies in the Swan Urban Growth Corridor (SUGC), particularly regarding the impact of tree removal and high groundwater levels. It seeks information on reviews, studies, and monitoring related to these issues.

(1) What reviews have been undertaken to determine the efficacy of drainage and water management strategies within the Swan Urban Growth Corridor (SUGC)?(2) What studies have been undertaken to determine the efficacy of the infiltration policy that underpins all drainage strategies within the Metro area with particular reference to areas of high groundwater?(3) Estimates indicate somewhere around 100,000 trees have been removed to date with another 60,000 when development is completed within the SUGC south of Gnangara Road. What studies have been undertaken to determine the impact of the removal of thousands of mature trees within the district where high groundwater is prevalent?(4) What studies have been undertaken to determine the efficacy of Water Sensitive Design, (formerly Water Sensitive Urban Design), technologies within areas of high groundwater?(5) Foundation documents such as the Swan Urban Growth Corridor Drainage and Water Management Plan 2009 (SUGCD&WMP 2009) that provide the blueprint for Drainage Strategies and Plans within the SUGC contain a number of measures to establish the effectiveness of Local Water Management Strategies. These include post-development monitoring as noted in SUGCD&WMP 2009 - 9.3 Monitoring strategy - Table 9-2 Assessment requirements of development proposals – monitoring, for a period of three years. Has monitoring inline with these requirements occurred for development or stages of development within the SUGC and where are the results?(6) Many adverse impacts related to drainage strategies in areas of high groundwater, such as rising groundwater, tree deaths due to continuous inundation, eutrophication of water resources and failure of infrastructure take many years to become apparent. The timeframe noted in the SUGCD&WMP 2009 for post-development monitoring is three years although a review of the drainage and management plan is required to be undertaken within 10 years or earlier if deemed necessary until development has occurred. Has any review of this plan been undertaken?(7) If no to (6), why not and when will this review be undertaken?(8) Development plans typically deal only with the footprint development will occupy and do not include offsite impacts. The attitude adopted is that stormwater and groundwater surplus to that deemed as required for environmental flows will be managed by containment on site to be disbursed via a combination of infiltration, biological processes, evaporation and release into receiving waters at a rate to mimic pre-development flows. This process is failing within the SUGC as evidenced by inundation and flooding of properties along the urban fringe. What actions are being taken to address this situation and when will it be remedied? (1) What reviews have been undertaken to determine the efficacy of drainage and water management strategies within the Swan Urban Growth Corridor (SUGC)? (2) What studies have been undertaken to determine the efficacy of the infiltration policy that underpins all drainage strategies within the Metro area with particular reference to areas of high groundwater? (3) Estimates indicate somewhere around 100,000 trees have been removed to date with another 60,000 when development is completed within the SUGC south of Gnangara Road. What studies have been undertaken to determine the impact of the removal of thousands of mature trees within the district where high groundwater is prevalent? (4) What studies have been undertaken to determine the efficacy of Water Sensitive Design, (formerly Water Sensitive Urban Design), technologies within areas of high groundwater? (5) Foundation documents such as the Swan Urban Growth Corridor Drainage and Water Management Plan 2009 (SUGCD&WMP 2009) that provide the blueprint for Drainage Strategies and Plans within the SUGC contain a number of measures to establish the effectiveness of Local Water Management Strategies. These include post-development monitoring as noted in SUGCD&WMP 2009 - 9.3 Monitoring strategy - Table 9-2 Assessment requirements of development proposals – monitoring, for a period of three years. Has monitoring inline with these requirements occurred for development or stages of development within the SUGC and where are the results? (6) Many adverse impacts related to drainage strategies in areas of high groundwater, such as rising groundwater, tree deaths due to continuous inundation, eutrophication of water resources and failure of infrastructure take many years to become apparent. The timeframe noted in the SUGCD&WMP 2009 for post-development monitoring is three years although a review of the drainage and management plan is required to be undertaken within 10 years or earlier if deemed necessary until development has occurred. Has any review of this plan been undertaken? (7) If no to (6), why not and when will this review be undertaken? (8) Development plans typically deal only with the footprint development will occupy and do not include offsite impacts. The attitude adopted is that stormwater and groundwater surplus to that deemed as required for environmental flows will be managed by containment on site to be disbursed via a combination of infiltration, biological processes, evaporation and release into receiving waters at a rate to mimic pre-development flows. This process is failing within the SUGC as evidenced by inundation and flooding of properties along the urban fringe. What actions are being taken to address this situation and when will it be remedied?