Land and Environment Court of New South Wales CITATION : Ni v Blacktown City Council [2009] NSWLEC 1112 APPLICANT Mei Hua Ni PARTIES : RESPONDENT Blacktown City Council FILE NUMBER(S) : 10961 of 2008 CORAM: Brown C KEY ISSUES: DEVELOPMENT APPLICATION :- demolition of all the existing structures on the site and the erection of a building for the purpose of a brothel - flooding LEGISLATION CITED: Environmental Planning and Assessment Act 1979 Blacktown Local Environmental Plan 1988 DATES OF HEARING: 16/12/08, 24/03/09 DATE OF JUDGMENT: 21 April 2009 APPLICANT Mr J Hannaford, solicitor SOLICITORS Hannaford Lawyers LEGAL REPRESENTATIVES: RESPONDENT Mr A Seton, solicitor SOLICITORS Marsdens JUDGMENT: THE LAND AND ENVIRONMENT COURT OF NEW SOUTH WALES Brown C 21 April 2009 10961 of 2008 Mei Hua Ni v Blacktown City Council JUDGMENT 1 COMMISSIONER: This is an appeal against the refusal by Blacktown City Council (the council) of Development Application No. 08-755 for the demolition of all the existing structures on the site and the erection of a building for the purpose of a brothel comprising 10 working rooms, waiting rooms, reception areas, office and the utility areas. A total of 19 car parking spaces are provided at the side and rear of the proposed building. 2 The single issue raised by the council was impact of flooding on the proposed new building and carpark. The site 3 The site is Lot 7 in DP 21261 and is located at 22 Tattersall Rd, Kings Park. It is irregular in shape with a total area of 1505 sq m and is partly subject to a 15 m Easement to Drain Water that affects the western and northern boundaries the site (and adjoining sites). The easement contains 3 x 2700 x 1200 mm reinforced concrete box culverts. The site is also potentially affected by overland flows resulting from flooding which is less than or equal to the 1% annual exceedance probability flood in circumstances where flows are unable to enter or be contained within the culvert system. 4 The site is occupied by a two-storey industrial building with a brick workshop to the rear of the site. The site is currently used for a mechanical repair business. 5 The surrounding area is industrial in nature with a mix of building forms and small automotive and light engineering activities to larger warehouses. Relevant planning requirements 6 The site is zoned 4(a) General Industrial under Blacktown Local Environmental Plan 1988 (LEP 1988). A brothel is a permissible use with consent within this zone although the council raised no issue with the use of the site as a brothel. Those parts of LEP 1988 relevant to the issue raised by the council are found in cl 20 - Development of land affected by that 1% annual exceedance probability flood. Clause 20(2) provides that the council may refuse consent to the carrying out of any development on land affected by the 1% annual exceedance probability flood where the development adversely affects the efficiency or unduly restricts the capacity of the of the floodway (cl 20(2)(a)), effects, to a substantial degree, the flow of flood water on adjoining lands (cl 20(2)(c)) or creates a hazard to life or property in time of flood (cl 20(2)(g)). 7 Blacktown Development Control Plan 2006 (the DCP) applies. Part 7 - Special Considerations provides requirements for drainage (Pt 7.4), Part 8 - Development on Flood Prone Land provides Aims and Objectives (Pt 8.2), Heads of Consideration (Pt 8.4.1), Development within the Floodway (Pt 8.4.2) and Part 9 Local Overland Flooding - Major Drainage and Local Runoff provides Aims and Objectives (Pt 9.2) and Control of Development on Land Subject to Local Overland Flooding (Pt 9.4). 8 Blacktown City Council Engineering Guide for Development 2005 also applies. Relevantly, cl 7.3(d) provides the maximum ponding depth for driveways and parking is 200 mm. The evidence 9 Mr Colin Fisher, an engineer, provided evidence for the applicant and Mr James Tsom, an engineer, provided evidence for the council. Mr Fisher and Mr Tsom agree on a number of fundamental aspects of the flooding, such as the 100 year annual recurrence interval (ARI) flow rate (71.8 cu.m/sec) and the capacity of the existing culvert system however they disagree on the conclusions that can be drawn from the HEC-RAS modelling undertaken by Mr Fisher. 10 Mr Fisher states that the HEC-RAS modelling indicates that the Romford Road formation acts as a hydraulic structure causing the 100 year ARI overland flow to split. The consequence is that overland flows are distributed between Romford Road (that distributes overland flows to Tattersall Road) and over the property known as "State Steel" and towards the existing easement. Accepting a flow rate of 71.8 cu.m/sec for the 100 year ARI storm event and 100% culvert blockage, the HEC-RAS model provides for 56.8 cu.m/sec overland flow on Romford Road and 15.0 cu.m/sec towards the existing easement. For a 0% culvert blockage, the HEC-RAS model provides for 30.8 cu.m/sec overland flow on Romford Road and 5.0 cu.m/sec towards the existing easement. 11 Mr Fisher states that the HEC-RAS model will yield results suitable for assessing the flood impact on the proposed development. In his opinion the results of his investigations correlate well with the recorded historical events and the findings of previous flood studies held by the council. 12 Based on a range of different scenarios, both pre-development and post development, Mr Fisher concludes that the proposed development will not adversely impact on neighbouring properties, flood waters over the car park will be maintained at a depth less than 200 mm, the velocity/depth product within the site will be below 0.4 and there will be a 49 cub m increase in flood storage capacity. 13 Mr Tsom is of the view that the proposed filling of the driveway area will reduce flood storage capacity within the floodway, reduce the capacity for the existing easement to act as an overland flow path and potentially divert floodwaters on to adjoining properties. Mr Tsom states that there are limitations in the one-dimensional HEC-RAS model used by Mr Fisher to model the complex overland flow behaviours and to properly determine flood depths and flow velocities due to potential lateral and backwater movements of flows caused by multiple obstructions in the overland flow path. In his opinion, flood behaviour should be assessed using a two-dimensional hydraulic model that allows lateral and backwater movements of flows to be properly considered. For these reasons, Mr Tsom does not accept that there is sufficient evidence to support the conclusions of Mr Fisher that the proposed development will not adversely impact on neighbouring properties and that overland flows will satisfy the acceptable criteria for the velocity/depth product and the depth of floodwater over the car park and consequent public safety. Findings 14 In balancing the opposing positions of Mr Fisher and Mr Tsom, I am more persuaded by the evidence of Mr Tsom. I agree with Mr Tsom that the total reliance on the HEC-RAS model by Mr Fisher is not without some doubt. The limitations explained to the Court by Mr Tsom are reinforced by comments in the Review and Assessment of Hydrological/Hydraulic Flood Models, published by the Department of Natural Resources 2006, where the model is described as " traditionally… used for simple flood studies with uncomplicated floodplains that can largely be described in 1D". The Floodplain Development Manual, April 2005 (Pt F5.3) also explains the limitations on 1D modelling. Based on the site view, the characteristics of the overland flowpath are far from uncomplicated because of the many and varied structures and obstructions that are located in this area. 15 In my view, the concerns of Mr Tsom have some foundation and there is uncertainty for the HEC-RAS model to accurately predict the complex overland flow characteristics that effect of the site and immediate areas. The HEC-RAS model outputs provide for a relatively small amount of overland flows towards the easement with the majority of the overland flow towards Romford Road under the different scenarios modelled by Mr Fisher. If there is some doubt over the modelling then there must be some doubt over the appropriate distribution of overland flows. Because of this uncertainty, the conclusions of Mr Fisher that the proposed development will not adversely impact on neighbouring properties, will achieve acceptable levels of ponding in the car park, will satisfy the appropriate velocity/depth product within the site of 0.4 and provide for an increase in flood storage capacity on the site are clearly questionable. The potential for greater ponding in the carpark and a higher velocity/depth product also raise the question of safety for occupants of the building. Clearly, a cautious approach is called for in this case as the proposal is for a new building and it could be expected that it will be in place for a relatively long period of time so it should be subject to a flood assessment that has a high level of certainty. 16 Mr Fisher also relies on a building design that is raised above the flood level to allow for the passage and storage of stormwater for his support. The plans, the subject of the appeal, provided for walls that extend to the ground and consequently do not allow for the passage and storage of stormwater. No leave was sought during the hearing to amend the development application plans. 17 I am also not satisfied that Mr Fisher provided any substantive evidence to confirm that the modelling results can be favourably compared with historical events and previous flood study data held by the council. 18 It would also seem that some consideration would needs to be given to the long-term overland flowpath. While there are multiple obstructions in the existing easement, these obstructions may not always exist through the future redevelopment of these sites (as was the case in this development). If the council maintains a similar approach to the protection of the drainage easement from obstructions as was done with this application, then it may well be that greater quantities of floodwater will use the overland flow path within the easement (rather than Romford Road). If this is the case, then the flooding impact on the site is likely to be underestimated even using Mr Fisher's modelling. 19 In accordance with cl 20(2) of LEP 1988, there is insufficient evidence to conclude that the proposed development will not adversely affect the efficiency or unduly restrict the capacity of the of the flood way (cl 20(2)(a)), effect, to a substantial degree, the flow of flood water on adjoining lands (cl 20(2)(c)) or create a hazard to life or property in time of flood (cl 20(2)(g)) and as such the development application must be refused. Orders 20 The Orders of the Court are: 1. The appeal is dismissed. 2. Development Application No. 08-755 for the demolition of all the existing structures on the site and the erection of a building for the purpose of a brothel at 22 Tattersall Rd, Kings Park is refused. 3. The exhibits are returned. _____________ G T Brown Commissioner of the Court DISCLAIMER - Every effort has been made to comply with suppression orders or statutory provisions prohibiting publication that may apply to this judgment or decision. The onus remains on any person using material in the judgment or decision to ensure that the intended use of that material does not breach any such order or provision. Further enquiries may be directed to the Registry of the Court or Tribunal in which it was generated.