Flood Emergency Response Plan - Bankwest Stadium
Flood Emergency Response Plan - Bankwest Stadium
MOLINO STEWART PTY LTD ABN 95 571 253 092 ACN 067 774 332 PO BOX 614, PARRAMATTA CBD BC, PARRAMATTA NSW 2124 TEL: (02) 9354 0300 FAX: (02) 9893 9806 www.molinostewart.com.au Bankwest Stadium FLOOD EMERGENCY RESPONSE PLAN for VenuesLive by Molino Stewart Pty Ltd ACN 067 774 332 MARCH 2019
ii VenuesLive DOCUMENT CONTROL Document Reference 1091 Bankwest Stadium FERP Report_Final_v2 Project Bankwest Stadium Document Type Flood Emergency Response Plan Author Filippo Dall’Osso, Steve Molino REVISION HISTORY Date Version Name Comments 08/03/2019 1 Filippo Dall’Osso Draft for Internal review 08/03/2019 1.1 Steven Molino Draft for Client review 08/03/2019 2 Steven Molino Final DOCUMENT APPROVAL For Molino Stewart Name Steven Molino Position Principal Venues Live Name Simon Davies Position General Manager Asset Management
Bankwest Stadium - Flood Emergency Response Plan iii CONTENTS 1 INTRODUCTION 1 1.1 Background 1 1.2 Site Details 1 1.2.1 Locality 1 1.2.2 Site Layout 1 1.2.3 Access 2 1.2.4 Topography 2 1.2.5 Operation 3 2 FLOOD BEHAVIOUR 10 2.1 Flood Generating Weather 10 2.2 Flood Probabilities 10 2.3 Flooding of the Site 10 2.3.1 Flood Extent and Levels 11 2.3.2 Frequency of Flooding 14 2.3.3 Flood Rate of Rise and Duration 14 3 FLOOD FORECASTS AND WARNINGS 15 3.1 Bureau of Meteorology (BoM) 15 3.2 Floodsmart 16 3.3 Observed Flood Levels 18 4 EMERGENCY PREPAREDNESS AND RESPONSE CONSIDERATIONS 19 4.1 Evacuation Modelling 19 4.1.1 Scope 19 4.1.2 Assumptions 19 4.1.3 Evacuation Time Needed 21 4.1.4 Evacuation Timeline 21 4.2 Consultation 22 4.2.1 Evacuation Challenges 23 4.2.2 SIP Challenges 24 5 FLOOD EMERGENCY RESPONSE PLAN 28 5.1 Emergency Response Philosophy 28 5.1.1 Priorities 28 5.1.2 Alert Modes 28 5.2 Responsibilities 30 5.2.1 NSW State Emergency Services 30 5.2.2 The Emergency Organisation Committee (ECO) 30 5.2.3 Chief Warden 31 5.2.4 Area Wardens and Wardens 31 5.2.5 Staff and Contractors 31
iv VenuesLive 5.2.6 Patrons, Entertainment Personnel and Media 31 5.3 Communication Methods 31 5.3.1 The Emergency Committee Organisation (ECO) 31 5.3.2 Chief Warden 32 5.3.3 Patrons 32 5.4 What do to Before, During and After a Flood 32 5.4.1 White Alert Mode – Normal Operations 32 5.4.2 Yellow Alert Mode 33 5.4.3 Orange Alert Mode 33 5.4.4 Red Alert Mode 35 5.4.5 Black Alert Mode 37 5.4.6 Green Alert Mode 41 REFERENCES 43 APPENDICES Appendix A – Flood Actions Checklist Appendix B – Emergency Contacts List LIST OF FIGURES Figure 1. Location of the site 4 Figure 2. Level L00 – Pitch and Services 5 Figure 3.
Level L01 - Concourse 6 Figure 4. North and East elevation 7 Figure 5. South and West elevation 8 Figure 6. Location of the 14m AHD topographic contour line with respect to level L00. 9 Figure 7. Flood depths and velocities in the 20% AEP event (adapted from CSS, 2018) 12 Figure 8. Flood extents and levels adopted by the City of Parramatta Council 12 Figure 9. Flood hazard adopted by the City of Parramatta Council 13 Figure 10. PMF hydrograph near O’Connell Street showing peak levels of the 5% and 1% AEP (in black) and floor levels at the site (in red) 14 Figure 11. Flood warning areas as defined in the Floodsmart war system 17 Figure 12.
Pedestrian Evacuation Route 21 Figure 13. Evacuation timeline and trigger levels plotted on the PMF hydrograph near O’Connell Street 23 Figure 14. Position of flood gates and retaining wall to water proof the southern access points to level L00 25 Figure 15.Estimated relationship between peak flood levels and Average Recurrence Interval of flood events upstream of O’Connell Street. 26
Bankwest Stadium - Flood Emergency Response Plan v LIST OF TABLES Table 1. Annual probabilities of a large flood happening while an event is taking place within the site 14 Table 2. Flood smart warning system: types of warning messages 16 Table 3. Flood warning types relevant to different items within the site as per the Floodsmart system 17 Table 4. Alert Mode Table setting triggers for each Alert Mode. A single trigger is necessary and sufficient to activate the relevant Alert Mode. 29
Bankwest Stadium - Flood Emergency Response Plan 1 1 INTRODUCTION 1.1 BACKGROUND VenuesLive Pty Ltd is taking over management of the Bankwest Stadium, due to finish construction in early 2019.
The stadium is located on O’Connell Street Parramatta, next to the Parramatta River, and has been previously known as Parramatta Stadium. The Stadium will seat 30,000 spectators, include five levels of premium, corporate and function spaces, and incorporate a range of food and beverage outlets. The stadium will predominately cater for sporting and community events but will also cater for concerts and functions.
Before operations can commence, a Flood Emergency Response Plan (FERP) must be completed and implemented as a condition of the development approval (DA condition D4.e). To satisfy the condition, the FERP must: Address evacuation, emergency access, flood warning and awareness, and refuge requirements within the site and any other relevant matters Be based on the flood levels supplied by Council and any additional local flood and flow path modelling that may be required Be prepared in consultation with the Council, the NSW State Emergency Services and NSW Fire and Rescue Be fully operational prior to the commencement of the use and must be maintained in operation perpetually.
VenuesLive engaged Molino Stewart to prepare this FERP to meet the above listed requirements.
In addition to this, while the objective of the consent condition is the protection to life, VenuesLive is also concerned about flood risks to property and profits. As such the FERP includes measures and actions to protect the facility itself, ensuring flood damage and associated recovery time is minimised. 1.2 SITE DETAILS 1.2.1 Locality The stadium is located in Parramatta, between O’Connell Street and the Parramatta River, north-west of the Marsden Weir. It is located on the parcels previously occupied by the demolished Parramatta Stadium and the Parramatta Pool.
It is bounded by the Parramatta Leagues Club and Eels Place to the north, O’Connell Street to the east, the Parramatta River to the south, the Old Kings Oval to the south-west, and the Parramatta River to the west and north-west (Figure 1).
1.2.2 Site Layout The stadium will include six levels, namely: L00 – Service level, located at a level of 9.12m AHD (Figure 2). L00 will include the playing field, a series of rooms and facilities located along the western side of the site, and four access tunnels connecting the pitch either directly to the outdoor area east of the stadium (i.e. the south east and north east tunnels), or to the indoor area along the western side of the site. Specifically, the rooms and facilities mentioned above will include: - The players and officials area, with lockers, showers, warm up space, medical and physio rooms, coaching rooms, and press conference room - A loading dock at the south-western corner, accessed via a road running along the southern end of the site to O’Connell Street - Media rooms and facilities - Kitchen an catering rooms and equipment - Staff rooms and facilities (lockers, uniform store, briefing rooms, communication facilities, computer room, DAS rooms, offices) - Security rooms (i.e.
security staff offices, breakout room, cash room) - Critical facilities, including the generator and tank room, main
2 VenuesLive switch room, waste management rooms, fire pump and valve room, air circulation room - Storage space. L01 - Concourse Level, located at a level of 14.67m AHD (Figure 3). This level includes a free flow walkway running along the south, east and north perimeter of the stadium and providing access to the seating area, as well as to toilet facilities, cafes and entry/exist gates. The western part of the concourse is gated and includes the VIP area with related facilities and function rooms. It should be noted that the ground level at all the entry/exit gates along the northern, western and eastern side of the stadium are about at the same level of the Concourse level (i.e.
a14.67m AHD), the gates on the southern and south eastern side of the stadium have external stairs going down to the level of L00 (i.e. 9.12m AHD).
L02 – the Club Level, at a level of 20.07m AHD. This level’s footprint, as well as all the levels above, occupies only the western part of the site. L02 includes rooms and facilities for the Directors’ Club. It can be accessed from the Concourse level via stairs or lifts. L03 – Suite Level, located at a level of 24.57m AHD, L03 occupies the same footprint as the Club Level. L03 includes 26 suites with access to private terraces overlooking the pitch. It also includes a kitchen area, and the executive offices. L04 and L05 - the Media Level and Media Roof level, located at a level of 29.07m AHD and 33.57m AHD respectively, including a camera deck, commentary rooms and additional suites.
L06 – Roof Level, at a level of 33.57 m AHD.
The open seating area will surround the playing field and extend from Level L00 (the playing field level) up to level L05. Figure 4 and Figure 5 show the stadium elevations. The site will incorporate a stormwater drainage system collecting rainwater falling over the whole footprint of the site (including the pitch and the roof) and discharging to the Parramatta River via the exiting stormwater drainage network. 1.2.3 Access The stadium will be accessible via O’Connell Street either by car or on foot. There will be two access driveways, north and south of the stadium, leading to three car parking areas, located north, west and south of the stadium.
The southern car park is not part of the Bank West Stadium site. Part of the southern car park is operated by Parramatta Park Trust and the remainder operated by Parramatta Council. Nevertheless, it is expected that the southern car park will be available to the stadium patrons during each event. The capacities of the car parks are: North - 292 West -187 South- 348 Total – 827 It is assumed that the large majority of patrons will access the site on foot and will arrive in Parramatta by public transport (bus, train or light rail) or drive and park remote from the site (street parking to the north and east or parking stations in Parramatta CBD).
The western car park will be predominantly used by sport players and performers, support staff, media and suppliers. The northern car park will accommodate VIP patrons and corporate patrons with access to suites. 1.2.4 Topography The overall topography of the site is sloping in a north-west to south-east direction, however it has been significantly altered locally by cut and fill operations associated with the construction works. The highest topographical level is just below 15m AHD nearby the River, at the northwestern end of the site, while the lowest point is in the southern car park at a level of 6.7m AHD.
The stadium will be built so that the northern end will have level L01 at ground level, while the south part will have level L00 at ground level (Figure 4 and Figure 5) Figure 6 shows the as-built contour line corresponding to 14m AHD, which is just
Bankwest Stadium - Flood Emergency Response Plan 3 above the reach of floodwaters in a Probable Maximum Flood (PMF). 1.2.5 Operation The stadium will host two types of activities: Events (i.e. activities utilising the playing field). It is anticipated that the stadium will host between 40 and 50 events per year with the number of patrons ranging between 10,000 and 30,000.
These will generally be sports competitions, during which patrons will occupy the seating area, the concourse level and the suites at the upper levels. Media will occupy the media areas and most other areas within the stadium will be used during these events. In addition to sport events there might be up to two music concerts per year, with up to 40,000 patrons each. In music concerts, the northern part of the seating area will be behind the stage and will have no patrons in it, resulting in a maximum of 25,000 patrons in the seating areas. However, there will be up to 15,000 patrons on the pitch at level L00.
There would be minimal vehicles in the stadium for events (less than 10) but the car parks around the perimeter of the stadium are expected to be full for every event. A typical event day would see stadium staff, players or performers, support staff and media arriving on site 2- 4 hours prior to the start of the event. Public entry gates will open approximately 2 hours before kick-off. Most sports events will last approx. 2 hours and the Stadium would be clear of all spectators within an hour of the end of the game.
Functions (i.e. smaller activities not utilising the playing field).
Functions could occur on any day of the year and there would be a maximum of about 800 patrons on site. These would held on level L02, L03 or L04. Function patrons would utilise the external car parks with minimal (less than 10) vehicles in the stadium. Aside from the above listed activities, the site will be operated from 7AM to 7PM Monday to Friday with up to 50 staff on site every day. Staff will enter either via the loading dock on level L00 or through the glass entry doors in the middle of the western stand on level L01. Weekends will see minimal staff on site unless an event or function is happening.
There will be a security presence on site 24/7 and several of the rooms and facilities on level L00 will be in use at all times.
Bankwest Stadium - Flood Emergency Response Plan 5 Figure 2. Level L00 – Pitch and Services
6 VenuesLive Figure 3. Level L01 - Concourse
Bankwest Stadium - Flood Emergency Response Plan 7 Figure 4. North and East elevation
8 VenuesLive Figure 5. South and West elevation
Bankwest Stadium - Flood Emergency Response Plan 9 Figure 6. Location of the 14m AHD topographic contour line with respect to level L00.
10 VenuesLive 2 FLOOD BEHAVIOUR 2.1 FLOOD GENERATING WEATHER Coastal areas of eastern Australia mostly receive flooding rains from so-called "east coast lows" that develop from time to time over the adjacent Tasman Sea. These are intense depressions off the coast and can produce thunderstorm activity associated with troughs. Depressions can develop at any time of year, but are most likely when sea surface temperatures are high and the air is humid. Therefore, these events usually occur in the summer months and over the first half of the year.
Flooding can also be a winter-spring phenomenon, associated with unusually frequent or active extra-tropical depressions and fronts.
However some major events have occurred in the summer half-year as systems of tropical origin extend or move south. Flooding over inland areas is usually associated with southward-moving tropical systems, but in the cooler months, may occur when well-developed cloud bands extend across the interior from the oceans north and northwest of Australia. Rainfall patterns are also dependant on longer term weather patterns. Flooding is more prevalent in a La Nina year when rainfall is significantly greater than the mean average rainfall. Thunderstorms, which generally occur during the summer, can also result in localised flooding which could impact specifically on the site.
2.2 FLOOD PROBABILITIES Flood probability can be expressed in more than one way. For example, a flood may be described as having a 1 in 100 year Average Recurrence Interval (ARI). This means that over many thousands of years, a flood of this magnitude would occur on average once in 100 years. This does not mean that a flood of this size only occurs once every 100 years. It is possible to have floods of this size in consecutive years or even two in the same year. This happened in several locations in Queensland and Victoria in 2010 and 2011. Another way of expressing flood probability is in terms of Annual Exceedance Probability (AEP).
A 100 year ARI flood has roughly a 1% AEP. That is, each and every year it has a 1% chance of being reached or exceeded. This is perhaps a more helpful way of thinking about flood probabilities, as it encapsulates the variability in the frequency with which similar flood events represent over time. A flood with a 1% AEP has about a 1 in 2 chance of being reached or exceeded in the average person’s life time, the same probability of tossing a coin and getting a head.
Bigger floods can and do occur. There were several floods with greater than a 1% AEP experienced in Eastern Australia in early 2011. Some reached levels which have a 1 in 2,000 (0.005%) AEP. A flood with a 1 in 500 (0.02%) AEP has about a 1 in 6 chance of being reached or exceeded in the average person’s life time, the same as tossing a dice and getting a 6. The largest flood that can possibly occur is referred to as the Probably Maximum Flood (PMF). Although it has a very low probability of occurring in any one year (1 in 1000,000 or less), events approaching a PMF have been recorded.
Flooding may occur at any time of year and at any time of day.
The most recent major floods in Parramatta – 1986 and 1988 – peaked in the afternoon and at night however there is no seasonality associated with flooding in Sydney and an event could occur at any time of day or night and on any day of the year. 2.3 FLOODING OF THE SITE Flooding of the site is primarily caused by the Parramatta River overtopping its banks, however minor flooding can also be caused by rainwater running across the ground (overland local flooding).
The flood information certificate provided by City of Parramatta Council (Figure 8 and Figure 9) shows that the site is flood affected in the Probable Maximum Flood(PMF). The
Bankwest Stadium - Flood Emergency Response Plan 11 site is not affected by floods as large as the 1% AEP event. This means that the site might flood to some extent only as a result of events with a probability smaller than 1% per year. The above information was obtained from the flood model currently in use at the City of Parramatta Council, which underpins the Upper Parramatta River Catchment Flood Study, undertaken by Bewsher Consulting in 2003.
The modelling uses a RAFTS-XP hydrologic model and a MIKE-11 hydraulic model. From the early 1990s the model was progressively updated to account for significant changes in the catchment including completion of flood mitigation works. However the software underpinning the model has now become obsolete and a new, more accurate model is being prepared by Council and the results are likely to be officially released in early 2020.
2.3.1 Flood Extent and Levels The flood information certificate provided by Council for the site does not include the exact flood levels for the 5% AEP, 1% AEP and PMF on site, as it usually does for smaller size developments. Instead, the certificate makes reference to the attached flood maps (Figure 8 and Figure 9), where flood levels for the above listed events are extracted at multiple cross sections of the Parramatta River, upstream and downstream of the site. The maps confirm that, according to the flood model currently used by Council, the site does not flood in the 1% AEP event, but is affected in the PMF.
However, the southern car park, which is as low 6.7m AHD, would be partly flooded in the 5% (1 in 20) AEP flood which reaches 7.02m AHD at cross section 1935 which is adjacent to the car park. The highest part of the car park is at 8.6m AHD and this is about 0.5m higher than the peak of the 1% AEP flood at this location (8.14m AHD). The format of the flood certificate provided by Council makes it difficult to obtain the exact peak flood level at the site in a PMF, because these vary along the river depending on the location of the cross section. However, a reasonable estimate of the PMF flood level at the site can be obtained by interpolating the levels upstream (profile 1021, PMF level of 13.8m AHD) and downstream of it (profile 1935, PMF level of 13.12m AHD).
Importantly, the flood extents showed in the map provided by Council would have been obtained using a topography surveyed when the old stadium was in place, however the construction of the new stadium will affect the local topography as a result of cut and fill operations.
Figure 6 shows the expected position of the 14m AHD contour line once the new stadium will be completed. Because the maximum PMF level will be 13.8m (upstream of the site), it is reasonable to expect that floodwaters would not be able to go past the 14m AHD contour line, meaning that the flood affectation of the site is likely to be smaller than what is shown in the flood maps. Flooding of the site is therefore likely to occur in two ways. Initially, the river will overtop its banks in the vicinity of O’Connell Street and rise through the southern car park towards the site. Given that level L00 is at 9.12m AHD, the maximum PMF depth at the southern end of the site would be between about 4m.
This would be sufficient to flood level L00 facilities and services, the pitch and all of the car parks.
However, at some point as the river is rising it would break its banks north and/or west of the site and flow around the site towards O’Connell Street where the topography is lower than the river level. For example, at the peak of a PMF, the river would be overflowing upstream of the site and would flow east along the site’s northern access road towards O’Connell Street at a depth of 0.5m or more. Once it reaches O’Connell Street it would flow south towards the river and join the flood waters which have reached the L00 level from the river rising to the south.
12 VenuesLive Figure 8.
Flood extents and levels adopted by the City of Parramatta Council
Bankwest Stadium - Flood Emergency Response Plan 13 Figure 9. Flood hazard adopted by the City of Parramatta Council
14 VenuesLive 2.3.2 Frequency of Flooding The information provided by Council does not allow to define exactly from which probability event the site would start flooding, however this would be significantly less frequent than the 1% AEP event. Although it is noted that the southern car park can begin flooding in events more frequent than the 5% AEP event. Importantly, the probability that a large flood occurs when a major event is taking place at the site is extremely low, ranging from 0.034% to 0.0000001%, depending on the event and the flood AEP (Table 1).
For reference, the probability of an individual being in a fatal car crash in Australia in year 2016 was 0.005%.(BITRE, 2018), which is about 1,500 times higher than the probability of the site experiencing a PMF during a 30,000 people sport event, and 36,500 times higher than this happening during a 40,000 people concert. However, it is acknowledged that the number of people at risk in the stadium during any individual event is at least 10,000 greater than the number of people in most car accidents. 2.3.3 Flood Rate of Rise and Duration Figure 10 shows the hydrograph of the PMF upstream of the Marsden Street weir extracted from the Upper Parramatta Mike 11 flood model.
The hydrograph shows the water level at a point along the Parramatta river between section 1733 and 1935 in Figure 8. The level at this point is about 0.2m higher than the gauge readings at the Marsden Weir.
This hydrograph was used in this study as a reference as it represents the worst case scenario of rate of rise in proximity to the site. Even in events smaller than the PMF, floodwaters could rise as fast as shown in this hydrograph. For reference, the peak levels of the 5% AEP and 1% AEP flood are also shown, as well as the levels of Level L00 and Level 01 at the site. The chart shows that in a flood rising as fast as the PMF, floodwaters would reach Level L00 after about 2h 20min from the beginning of the rainfall, and that level would be isolated for up to 5 hours.
Table 1. Annual probabilities of a large flood happening while an event is taking place within the site No.
of events per year 1% AEP (the site is flood free) PMF 30k patrons sport event Up to 50 0.034% 0.0000034% 40k patrons concert Up to 2 0.001% 0.0000001% Figure 10. PMF hydrograph near O’Connell Street showing peak levels of the 5% and 1% AEP (in black) and floor levels at the site (in red)
Bankwest Stadium - Flood Emergency Response Plan 15 3 FLOOD FORECASTS AND WARNINGS Monitoring the weather forecasts and warnings will be an integral step in managing the flood risk of the site. This will be critical to being able to evacuate the site before flooding commences. 3.1 BUREAU OF METEOROLOGY (BOM) The Bureau of Meteorology (BoM) has a number of generalised warning products that could provide an indication of an increased flood threat: Severe Weather Warnings. The Bureau of Meteorology (BoM) issues Severe Weather Warnings whenever severe weather is occurring in an area or is expected to move into an area.
The warnings describe the area under threat and the expected hazards. Warnings are issued with varying lead-times, depending on the weather situation, and range from just an hour or two to 24 hours or sometimes more. The key subtype of Severe Weather Warning to be monitored for the site are warnings with reference to flash flooding for the Sydney Metropolitan Area. These are issued directly to the media by the BoM when there is a high probability of flash flooding as a result of intense rainfall. Severe Weather Warnings may also include other conditions such as damaging winds. New South Wales weather warnings are issued by the BoM and can be found at the following link: www.bom.gov.au/nsw/warnings/ and access the relevant warning; Severe Thunderstorm Warnings.
A severe thunderstorm may produce intense rain and flash floods, hail, damaging winds, and even tornadoes. The BoM provides two types of Severe Thunderstorm Warnings: - Detailed Severe Thunderstorm Warnings. These are issued for capital cities only with up to 60 minutes of notice, and provide more specific information on individual severe thunderstorm locations; - Broad-based State-wide Warnings. These are based on broad areas such as the Bureau's weather forecast districts, and are issued with up to 3 hours’ notice. A Flood Watch for the Parramatta River area.
A Flood Watch is a “heads-up” that flood producing rainfall is forecast and flooding may eventuate. These are usually issued one or two days in advance of the expected flooding and about 25% of the time flooding does not eventuate. In addition to the above listed warning products, the BoM has forecast rainfall maps which can be used to estimate the amount of rain expected to fall over the next eight and four days, as well as the next 24 hours. This information is available at the following website: http://www.bom.gov.au/jsp/watl/rainfall/pme.jsp The radar service on the BoM website also shows current rainfall locations and intensities.
The radar station to be used for the site would be the Sydney Terrey Hills Radar (http://www.bom.gov.au/products/IDR714.loop. shtml#skip).
The Bureau of Meteorology also has rainfall and river gauges which show the amount of rainfall that has fallen in the previous 24 hour period and stream gauges which indicate water heights. The closest river gauge is located at the Marsden Weir. Live readings of the river level can be seen at this webpage: Plot version: http://www.bom.gov.au/fwo/IDN60233/IDN602 33.567107.plt.shtml Tabulated version: http://www.bom.gov.au/fwo/IDN60233/IDN602 33.567107.tbl.shtml In order to relate the gauge readings to the hydrograph shown in Figure 10, an offset of 3.94m should be used to account for the fact that the gauge zero is 3.74m AHD and that in floods there is a slope on the water surface from upstream of the O’Connell Street bridge to the gauge at Marsden Weir of about 0.2m.
16 VenuesLive For instance, if the gauge reading is 0.5m, the actual flood level will be: Flood level AHD = gauge reading + 3.94m =0.5m+3.94m= 4.44m AHD 3.2 FLOODSMART In addition to the information provided by the BoM, the City of Parramatta Council has recently put in place a local flood warning system which is freely available to anyone subscribing to the service. The system is called “Floodsmart” and can be accessed at the following link: https://www.cityofparramatta.nsw.gov.au/recre ation-environment/floodsmartparramatta/flood-warning-service Floodsmart provides flood early warning messages via text, email, or automated voice message.
The system includes seven different warning areas covering Parramatta LGA. The area relevant to the Bankwest stadium is “Westmead and North Parramatta”. The types of flood warnings provided are summarised in Table 2.
Table 2. Flood smart warning system: types of warning messages Type of Warning Message Description MINOR: High risk areas may experience property flooding Risk to life from fast flowing or deep water near the river or creek Closure of roads most at risk of flooding Flooding of land near rivers, creeks, low spots and recreational areas Water levels may be high for many hours MODERATE: High and Medium risk areas may experience property flooding. High risk to life from fast-flowing or deep water near the river or creek Closure of many bridges and roads Widespread flooding in areas not necessarily near the river Water levels may be high for many hours MAJOR: High, Medium and Low risk areas may experience property flooding Damage is possible to buildings and infrastructure Extreme risk to life from fast-lowing deep water even in areas not near the river or creek Closure of many bridges, roads and transport routes Widespread deep flooding in many areas not necessarily near the river Water levels may be high for many hours NO FURTHER IMPACT The local conditions should now be improving: No further flooding is expected in the next 12 hours Flood levels will continue to drop However: There may still be dangerous fast flowing water near the river or creek Debris and contamination may still cause problems in areas that have been flooded
Bankwest Stadium - Flood Emergency Response Plan 17 According to Council’s classification of flood warning areas (Figure 11), the stadium is classified as a development at LOW RISK of flooding. As such, it is at risk of flooding only during a MAJOR flood. However the southern car park is classified as being at MEDIUM RISK and it may experience flooding in a MODERATE flood (Table 3). Floodsmart warnings can be issued with a maximum notice of up to 2 hours, however in rapidly evolving circumstances the warning notice may be shorter.
Table 3. Flood warning types relevant to different items within the site as per the Floodsmart system Element at risk Flood Warning Area Classification Relevant Flood Warnings Stadium, including northern and western car parks and access driveway LOW RISK MAJOR, NO FURTHER IMPACT Southern car park MEDIUM RISK MODERATE, MAJOR, NO FURTHER IMPACT Figure 11.
Flood warning areas as defined in the Floodsmart war system
18 VenuesLive 3.3 OBSERVED FLOOD LEVELS While the BoM and Council have several products which can provide some advanced warning of potential or actual flooding or provide real time data on actual rainfall intensities and river levels, this data may not be accessible during a flood. This may be because the severe storms or flooding damage the gauges or they damage the telecommunications or electricity infrastructure needed to transmit data and disseminate warnings, or there may be human error in interpreting data and issuing warnings. It will therefore also be important to visually monitor water levels in the river.
This would most easily be done from the southern end of the concourse level looking over the southern car park.
Bankwest Stadium - Flood Emergency Response Plan 19 4 EMERGENCY PREPAREDNESS AND RESPONSE CONSIDERATIONS The two main types of responses to a flood emergency are to either: Evacuate to an area above the reach of floodwaters. This is the NSW SES preferred response, provided that the risks of evacuating are deemed acceptable; Take Shelter in Place (SIP) (i.e. within the Stadium) and wait until floodwaters have receded and the emergency has passed. SIP is to be considered an alternative to evacuation only when the risks of evacuating are higher than the risks of SIP.
Both evacuation and SIP were considered as possible flood emergency response strategies in this FERP.
This Section provides a summary of the flood emergency response analysis (for evacuation and SIP) that was undertaken as part of this FERP to inform the identification of the most suitable response strategy and management actions. The analysis was undertaken using a worst possible scenario approach. Namely, it was assumed that the worst possible flood (i.e. the Probable Maximum Flood, or PMF) would occur during the largest possible event that will be held at the Stadium (i.e. a 40,000 patron concert). However it should be emphasized that flood emergencies are more likely to occur during normal operating hours (Monday to Friday, 7AM to 7 PM), when only up to 50 staff will be onsite, or during the night, when only security will be on site.
Furthermore, most flood emergencies will be much smaller events than the PMF.
However, by having a FERP which can cater for the largest event in the largest flood, all floods can be appropriately responded to at any time. 4.1 EVACUATION MODELLING 4.1.1 Scope An assessment of the evacuation time in the largest possible site event was undertaken to understand if: Evacuation would be possible at all before evacuation routes are cut by floodwaters in a PMF; At what point in time an evacuation order would need to be issued to provide enough notice for all patrons and staff to leave the site before evacuation routes are cut; and How often, on average, floodwaters would reach the level selected as a trigger for evacuation.
It should be noted that even if the evacuation trigger level is reached and an evacuation order is issued, in most instances floodwaters would stop rising before affecting the site or cutting evacuation routes. However in extremely rare circumstances floodwaters would keep rising to the peak of the PMF and would isolate the site. During a real event it will not be possible to know with sufficient notice when floodwaters will stop rising after the evacuation trigger level is reached. It was therefore deemed desirable that the evacuation trigger level is not reached too often (ideally less often the once every 20 years).
Because in each large event several hundred patrons would reach the site by car, evacuation was modelled as a combination of pedestrian and vehicular evacuation. 4.1.2 Assumptions The following assumptions were used: The event would host 40,000 patrons, of which 15,000 would be in the pitch and 25,000 in the seating areas; Management would take about 10 minutes to decide to evacuate and disseminate an evacuation order after they become aware that the trigger level has been reached; To avoid traffic delays due to pedestrians blocking access to the road to vehicles and vice versa, pedestrian evacuation
20 VenuesLive would begin only when vehicular evacuation has completed. Patrons would decide to evacuate immediately after an evacuation order is issued; In line with the assumption of the Stadium Emergency Management and Response Plan, it would take up to 8 minutes for anyone in the stadium’s seating area to reach the Concourse level from the moment they decided to evacuate after an evacuation order has been issued. Once on the concourse there would be no further bottlenecks within the stadium to slow down the flow of evacuees (i.e. free flow); Patrons on the pitch would be able to evacuate by either walking up to the Concourse level (L01) using the aisles in between seats (20 aisles would be available to do so), or walking through the north-east and north-west tunnels at the relevant corners of the pitch.
Because the south-east and south-west tunnels terminate at level L00 (i.e. 9.12m AHD), these will be cut earlier that all the other exits and as such it was assumed that these tunnels will be closed during an evacuation. This means that patrons in the pitch would take an extra couple of minutes to reach the Concourse level or to exit the stadium though the north-east tunnel in addition to the 8 minutes mentioned above.
Further assumptions applying to pedestrian evacuation only: Pedestrians would exit the site either from the north-east gate at the Concourse level or from the north-east tunnel as these exit points are the closest to a flood free area in the PMF. Pedestrians would then continue walking north along O’Connell St up to the crossroad with Ross St, where some of them would continue on Ross St (Figure 12); The bottleneck along the pedestrian evacuation route would be in O’Connell St, immediately north of the stadium’s north-east gate. About 40,000 people would need to walk past this point in an evacuation.
The road width here is 22m (footpaths plus road), but it was conservatively assumed that only 20m would be available for evacuation; In line with the relevant literature on pedestrian evacuation (Seyfried et al., 2005), pedestrians would be able to move at a speed of at least 700 metres per hour, with a density of up to two people per square metre through the concourse and in areas external to the stadium. Further assumptions regarding vehicular evacuation only: People evacuating by car would exit the stadium using the closest exit to the relevant car park and would take about 10 minutes to reach their cars after leaving their seats, as they would need to walk a maximum distance of 500m; All car parking spots would be occupied in any event.
These equate to the following number of cars: - Northern car park - 292 - Western car park -187 - Southern car park- 348 - Total – 827 In line with the assumptions of the NSW SES Timeline Evacuation Model (Opper et al, 2009), vehicular evacuation would proceed at a speed of 600 cars per lane per hour; All cars in the southern car park would leave the site from the south driveway and move north along O’Connell St or east along Victoria Rd, then north on Villiers St; All cars parked in the western and northern car parks (total of 479 cars) would leave the site from the northern driveway and move north on O’Connell Street up to Grose St, then continue in O’Connell St and Grose St; Each driveway would have two lanes available to exit the car park during a flood emergency.
Bankwest Stadium - Flood Emergency Response Plan 21 4.1.3 Evacuation Time Needed Under the assumptions listed in previous section, the following evacuation times were obtained. a) Pedestrians It would take 1h 25m for 40,000 pedestrians to walk past the bottleneck in O’Connell Street and reach a flood-free area; The total pedestrian evacuation time, including 10 min for Management to decide to issue the evacuation order and 8-10 min for patrons to walk to the Concourse level, would be 1h 45 min. b) Cars The 349 cars in the southern car park would take 17 minutes to clear. The total evacuation time for this car park, including 10 min for Management to decide to issue the evacuation order, 8 min for patrons to walk to the Concourse level and 10 additional min to walk to the car, would be 45min.
The 479 cars in the northern and western car parks would take 24 minutes to clear. The total evacuation time for this car park, including 10 min for Management to decide to issue the evacuation order, 8 min for patrons to walk to the Concourse level and 10 additional min to walk to the car, would be 52min. 4.1.4 Evacuation Timeline An evacuation timeline is usually defined by: Identifying the hydrograph of the worst possible flood event (the PMF) at a known location nearby the site. This is shown in Figure 10 and Figure 13. Identifying the level of the lowest point along the evacuation route; Using the hydrographs, identifying the time at which the lowest point is cut by floodwaters; Figure 12.
Pedestrian Evacuation Route
22 VenuesLive Subtracting the total evacuation time from the time at which the evacuation route is cut to identify the time at which evacuation should begin; Identifying the level of floodwaters at the time evacuation should begin to set the evacuation trigger. In this case, given the large size of the site and the fact that the local topography ranges between 6.7m AHD and 15m AHD, two evacuation routes were identified (one vehicular only for cars in the southern car park, the other one both pedestrian and vehicular, for cars in the western and northern car parks and for all patrons on foot).
The lowest point of each route is at very different levels and they are each impacted by flooding rising in the river at different locations. The lowest point along the evacuation route from the southern car park is within the car park itself, at its south-east corner, at a level of 6.7m AHD. This is flooded from water rising in the river at O’Connell Street at the location where the hydrograph in Figure 13 has been extracted from the model. These river levels are about 0.2m higher than the corresponding levels at the Marsden Weir about 200m downstream.
The lowest point along the evacuation route from the western and northern car parks, as well as along the pedestrian evacuation route, is near the junction between the northern driveway and O’Connell Street, at a level of 13.25m AHD.
This is first affected by flooding from water breaking out of the river north of the stadium about 1km upstream of O’Connell Street. Water levels at this point are about 0.5m higher than at O’Connell Street in large floods. The significant difference in ground levels between these two low points and the river levels which affect them means that the two evacuation routes would be cut at very different times during a flood. Namely, the southern car park will flood much earlier and more frequently than the northern driveway. In these circumstances, having a single evacuation trigger for the whole site would be highly impractical, because in most flood events that trigger an evacuation only the southern car park would end up flooding (if at all).
As such, it was decided to evacuate the site in three stages, each one having its own trigger: 1. A first evacuation order would be triggered only for patrons who have parked their cars in the southern car park, which is the first to flood; 2. If floodwaters continue to rise, a second evacuation order would be triggered only for patrons who have parked their cars in the western and northern car park; 3. Once vehicular evacuation is completed, if floodwaters have continued to rise, pedestrian evacuation would be triggered. Alternatively, pedestrians could remain within the stadium (SIP) until floodwaters have receded.
A timeline of the above described evacuation process was generated and associated to the hydrograph of the PMF near O’Connell Street (Figure 10). This was achieved using the total evacuation times calculated in Section 4.2.3 to work backwards from the moment when evacuation routes are cut and identify the relevant evacuation trigger levels and times. The resulting evacuation timeline is shown in Figure 13.
4.2 CONSULTATION The evacuation modelling results, assumptions and timeline described in Section 4.2 were presented and discussed in a face to face meeting with: A representative from the NSW SES; The Local Emergency Management Officer, who is the liaison officer for all hazards in Parramatta LGA, including floods and fires ; A representative from Council’s Development Applications Office; VenuesLive’s General Manager; Molino Stewart’s flood engineers.
23 VenuesLive During the meeting the challenges of evacuation and shelter in place for the site were identified.
A series of measures to address these challenges were also proposed, discussed and approved. These are summarised in the following sub-sections. 4.2.1 Evacuation Challenges The following challenges of the proposed evacuation strategy and timeline were identified: a) Evacuation of Southern Car Park Even though the proposed staged evacuation strategy would avoid unnecessary and frequent evacuations of all patrons on site, evacuation of the southern car park would still be triggered very often. In fact, the trigger level at the Marsden Weir gauge would be 4.3m AHD, and the average level at this gauge is about 4.2m AHD, meaning that a small fluctuation in level would trigger evacuation of the car park.
Moreover, issuing an evacuation order only for patrons who have their cars in the southern car park would likely cause concern, if not panic, among all the other patrons. Finally, patrons who have their cars in the southern car park would need to walk from a lower risk zone (i.e. the stadium) to a higher risk zone (i.e. the car park). Any unforeseen delays in the evacuation could result in patrons reaching the car park when this is already flooding. To address these challenges, the NSW SES proposed to close access to the southern car park before the event, if the available flood forecasts suggest that a flood large enough to affect the car park may occur within a few hours.
This suggestion was implemented in this FERP by creating a series of Alert Modes and triggers (refer to Section 5.1). b) Flooding of Level L00 from Southern Gates In a flood rising as fast as the PMF, floodwaters would start entering Level L00 about 20-30 minutes after the pedestrian evacuation order is issued. At that point in time all patrons at level L00 should have already evacuated, but any delays may result in patrons becoming in contact with floodwaters. Figure 13. Evacuation timeline and trigger levels plotted on the PMF hydrograph near O’Connell Street
24 VenuesLive In addition to this, Level L00 contains a large part of the infrastructure and facilities that will need to be fully operative during a flood emergency (e.g. power generator and fuel tank, electric power main switches, fire pump, security rooms). These issues will be addressed by water proofing the two southern access points to level L00 with two 2.4 m high automatic flood gates. The western gate will also require a retaining wall along the road connecting the southern driveway to the western car park (Figure 14). The retaining wall will have the same height as the flood gate (i.e.
2.4m AHD). The gates and retaining wall will be coupled with a series of automated backflow blocking devices to be placed along all drainage pipes connecting the stadium to the river. This system will protect level L00 up to a level of 11.52m AHD. Based on the flood levels provided by Council, it was estimated that this level corresponds approximately to a 1 in 50,000 year average recurrence interval (ARI) flood (Figure 15).
c) Risk of Pedestrians Evacuating South As discussed in Section 4.2, once they have left the site all evacuees would have to head north on O’Connell Street, because there is a risk that at that point O’Connell Street will already be cut by floodwaters in proximity to the river, or that most roads in the CBD will be cut by local flooding. However patrons who will reach the site on foot will likely arrive at Parramatta by train or bus, and both the train station and the bus interchange are located south of the river. Other patrons may decide to drive and park their cars in one of the covered secure car parks in the CBD.
These patrons, when asked to evacuate, would naturally go home in the same way they arrived to Parramatta, and would therefore try and walk south on O’Connell Street and cross the river. This risk will be addressed by ensuring that when pedestrian evacuation commences, there is a sufficient number of staff in O’Connell Street advising evacuees to walk north.
d) Where to Evacuate? Even if all pedestrians evacuated north using the designated evacuation route, there would be no suitable facilities within walking distance to receive such a large number of people. Evacuees would most likely have to wait in the streets until floodwaters withdraw, under intense rain and without any of the services that the stadium would have otherwise provided (e.g. shelter, sustenance, access to toilets, access to information, access to medical aid). This may expose evacuees to risks that could be deemed higher than the risks associated with taking shelter within the stadium.
This issue was discussed during the consultation meeting and it was agreed that the most appropriate solution would be to offer patrons the choice to either evacuate or shelter in place. This will be done by providing suitable information to patrons regarding the implications of evacuating or taking shelter in place. This information will be provided via emergency messages issued via the PA system. 4.2.2 SIP Challenges If patrons made the decision to take shelter within the stadium until the emergency has passed, in the worst possible scenario they would be isolated by floodwaters for about 2h 40min (Figure 13).
In addition to the relatively short isolation time, the maximum water depth along the evacuation route would be around 0.5m. While it is widely acknowledged that there are risks associated with taking shelter in place, these are generally greater for longer isolation times. Nevertheless, the risks of SIP were identified and addressed as part of this FERP. These include: