Environment Waikato Internal Series 2002/08
Flood Warning Procedures Manual 2003
Distribution List (controlled copies):
Hamilton Incumbent Level 1 Emergency Management Officer (EMO) Incumbent Level 2 Emergency Management Officer (EMO) Natural Hazards and Emergency Management Officer (working copy only)
Paeroa Hazard Liaison Officer (HLO) Taupo Hazard Liaison Officer (HLO)
Prepared by: Adam Munro Peter Mora
For: Environment Waikato PO Box 4010 HAMILTON EAST
4 February 2003
Document #: 761111
Environment Waikato: Incoming Call or Query Emergency Management Response Procedures
Phone: 025 992 120 Emergency Pager: 026 257 4456 Management Duty Freephone: 0800 800 401 Officer EMO2 Ph: 027 229 2958 Assess nature of call
Civil Defence
Flood (e.g. volcanic eruption, Marine Oil
Warning earthquakes etc) Spills
As per the EMO Notify Duty As per the EMO Roster Roster On-Scene Commander
Scott Fowlds Ph. 07 855 6503 or 0274 980 803 Guy Russell Ph 07 855 9398 Murray Mulholland Ph 07 858 4994 For Freshwater (inland) Spills, refer caller to: RUG – Pollution Response Ph 0800 800 401
External Emergency Contacts: MRP CC MRP Flow Genesis CC Genesis Flow Phone Phone Ph (07) 857 0110 (0800) 820 082 (07) 386 8615 (07) 386 8113 (07) 386 1212 – Dennis Drinkrow (021) 835 483
IGNS (for Earthquake and Volcanic Activity) Rostered Duty Scientist Ph 04 570 1444 or 07 376 0155
Dept of Conservation Duty Officer Ph 025 905 830 Hot-line: 0800 362 468
Maritime Safety Authority (for Marine Oil Spills) Marine Duty Officer Ph 04 472 7367 or 025 439 508 Pgr 026 816 159
Sandbags Thompson Sack Company Ph 07 889 6960 ProLife Foods (Nikho van der Zwet) Ph 834 3333 ext 711
Councils (out of region) Environment BoP Ph 07 307 2545 (office hours only) Rotorua District Council Ph 07 350 0172 Auckland Regional Council Ph 025 770 922 (Ian Wood) or 0800 806 040
Transit NZ Information Line Ph 0800 44 44 49 NZ Fire Service (Rob Saunders) (07) 834 1700 (025) 822 215 Police (John Kelly) (027) 243 1494 Federated Farmers (John Fisher) (07) 827 3628 or (025) 356 020
Flood Warning Procedures Manual 2003 Page i Councillor Phone/Fax Numbers Councillor Phone Numbers Fax Numbers L B Burdett Home Ph: 07 378 3025 Home Fax: 07 378 3025 (Laurie) I Balme Home Ph: 07 829 8855 Home Fax: 07 829 8845 (Ian) 027 471 9920 RE Hawkins 07 378 9358 Home Fax: 07 378 9357 (Rex & Sue) 027 296 3695 J D Howland Home Ph: 07 883 8995 Home Fax: 07 883 8994 (Jim & Elizabeth) Cellphone: 0274 715 560 AW Hinds 07 866 3981 Home Fax: 07 866 3981 (Arthur) 021 901 167 L A Livingston Hamilton Ph: 07 856 6952 Home Fax: 09 425 6036 (Lois) Warkworth Ph: 09 425 6035 Cellphone: 0274 867 188 A J Macdonald Home Ph: 07 824 7094 Home Fax: 07 824 7894 (Angus & Ruth) Cellphone: 025 343 685 BJ Morrison 07 863 6344 Home Fax: 07 862 6348 (Basil) 027 494 6403 R A Neely Home Ph: 07 873 6946 Home Fax: 07 873 6956 (Andra & Lance) Cellphone: 021 133 6086 B M O’Connor Home Ph: 07 825 9858 Home Fax: 07 825 9862 (Barry & Josie) Cellphone: 0274 854 480 S C Osborne Home Ph: 07 887 3830 Home Fax: 07 887 3830 (Steve & Judy) Cellphone: 025 380 102 D J M Peart Home Ph: 07 847 6319 Home Fax: 07 846 7322 (David & Heather) Cellphone: 0274 843 765 P A Southgate Home Ph: 07 856 1470 Home Fax: 07 856 6156 (Paula & Ross McNeil) J A Vernon Home Ph: 07 825 688 Home Fax: 07 825 8168 (Jenni & Gordon) Cellphone: 025 967 288
Page ii Doc # 761111 Overview of the Waikato/Waipa River System
WAIKATO RIVER WAIPA RIVER
Tributaries TPD Otewa
Te Kuiti LAKE TAUPO
Control Gates
Taupo Catchment Otorohanga
Mt Pirongia Trib inflows Puniu
Karapiro
Hydro System
Trib inflows
Whatawhata Hamilton
Lower Waikato Ngaruawahia
Mangawara
Huntly
La ke Waikare Rangiriri Spillway Trib inflows
Whangamarino Control Gates
Mercer Mangatangi Mangatawhiri
Flood Warning Procedures Manual 2003 Page iii Overview of the Piako/Waihou River System
Waihou River Piako River
Okauia
Kiwitahi
Shaftesbury
Morrinsville
Te Aroha Paeroa-Tahuna Rd
Mangaiti Stm Waitawheta R. Waitoa River
Waharoa Tirohia
Ohinemuri Mellon Road Paeroa River
Hikutaia R. Maukoro Landing
Matatoki Stm
Kirikiri Stm Flax Block ponding zones
Mangakirikiri Stream
Ngatea Thames Kauaeranga River
Firth of Thames
Page iv Doc # 761111 Flood Warning Procedures Manual
Record of Amendments Amendment Number: Amendment Date: Entered by:
Flood Warning Procedures Manual 2003 Page v Why does Environment Waikato provide Flood Warnings? Flooding is a major hazard in the Waikato Region due to:
• The presence of 20 major and 1420 minor river systems
• It’s location makes it susceptible to storms of tropical origin
• Steep gradients in many of the region’s river catchments promotes “flash flooding” and increased runoff rates
• There are large areas of low-lying flood plains below, at, or just above sea-level that are intensely farmed (see Figure 1)
• There are large areas of land lacking vegetation cover – increasing run-off and erosion
What difference does the Flood Warning System make? Without an operative flood warning system in place, flood management with electricity generators would be difficult and more complex, there would be more reliance on local knowledge, un-necessary pre-emptive actions could be taken (costly), community concern would be much higher, resources could be stretched, mis-information to District Council’s could occur, and inadequate media reporting could all contribute to a less than effective flood response.
Legislative Requirements Environment Waikato has a mandate under two acts of parliament to monitor waterways for floods. The Soil Conservation and Rivers Control Act 1941 states that regional councils (ex Catchment Boards) should prevent/minimise damage by floods, and the Resource Management Act 1991 gives regional councils functions to control the use of land for avoidance and/or mitigation of natural hazards.
Environment Waikato is also very active in flood forecasting, carrying over many of the functions of its predecessor, the Waikato Catchment Board. Hence, behind the legislative requirements, experience, resources and assets play a vital role in Environment Waikato’s continued involvement in flood warning.
The MetService provides a weather forecasting service, and issues severe weather warnings to assist in the management of river floods.
In the last 25 years. There have been several major floods and a number of minor events recorded throughout the region. The more significant of these occurred in 1976 (Ohinemuri River), 1981 (Ohinemuri River), 1985 (Kauaeranga River), 1995 (Lower Waikato River), 1997 (Cyclone Fergus, Tairua River), and July 1998 (Lower Waikato Flood Event). Generally, flood events have been experienced throughout the region in all 20 major river systems and have affected both urban and rural communities.
For further information, refer to the “Natural Hazard Impact and Priorities – Overview Report 1998” by D. Parkin.
Page vi Doc # 761111
Figure 1: Main aeas in the Waikato Region at risk from flooding
Flood Warning Procedures Manual 2003 Page vii Purpose of Manual This Flood Manual comprises a set of instructions and supporting information that sets out the responsibilities for action, reporting, decision making, and liaison in the event of a flood in the Waikato Region. The purpose of this manual is to illustrate procedures and define the implementation of systems and human resources. The Natural Hazards/Emergency Management Programme Manager is responsible for planning, maintaining, and implementing this Flood Manual and for training Environment Waikato Staff in the procedures required for operational response measures.
The concept of flood management for Environment Waikato is that information and warnings received into Environment Waikato’s Hamilton Office at any time are to be brought to the immediate attention of the incumbent Level 1 Emergency Management Officer (EMO). The Level 1 EMO is the appointed Environment Waikato Flood Manager and is responsible for co-ordinating and controlling all Environment Waikato operational matters pertaining to flood events in the Waikato Region.
Page viii Doc # 761111 Table of Contents Flood Warning Procedures Manual 2003...... 1 External Emergency Contacts: ...... i Councillor Phone/Fax Numbers ...... ii Flood Warning Procedures Manual...... iv Flood Warning Procedures Manual...... v Record of Amendments...... v Why does Environment Waikato provide Flood Warnings? ...... vi Purpose of Manual...... viii The Purpose and Objectives of Flood Warning...... 1 Customers ...... 2 Content of Flood Warnings ...... 3 The Flood Warning Team ...... 5 Management Procedures...... 6 Civil Defence Warning System Test Messages ...... 7 Territorial Authorities – Contact Information...... 8 Appendix A ...... 9 Action Plans - All Catchments...... 9 Ohinemuri River - Procedures...... 9 Background Information ...... 9 The river today...... 10 Ohinemuri ...... 10 Why provide Flood Warnings? ...... 11 Flood Procedures (Ohinemuri River at Karangahake) ...... 12 Ringing List No.1 ...... 15 Specified Levels...... 15 Ohinemuri River at Karangahake Return Periods ...... 15 Kauaeranga River – Procedures...... 16 Background Information ...... 16 Why provide Flood Warnings? ...... 16 Flood Procedures (Kauaeranga River at Smiths)...... 17 Floodway Capacities...... 20 Kauaeranga at Smiths Return Periods...... 21 Waihou River - Procedures...... 22 Background Information ...... 22 Why provide Flood Warnings? ...... 22 Methods for Predicting Levels ...... 23 Flood Procedures (Waihou River at Okauia)...... 23 Flood Procedures (Waihou River at Te Aroha) ...... 24 Flood Procedures (Waihou River at Tirohia)...... 27 Ringing List No. 1 ...... 27 Ringing List No.2 ...... 28 Ringing List No.3 ...... 29 Flood Procedures (Waihou River at Puke Bridge) ...... 30 Flood Procedures (Waihou River at Pekapeka)...... 30 Approximate Annual Levels: ...... 30 Floodway Capacities...... 30 Waihou River at Te Aroha – Return Periods (figures from 1998 rating review summary) ...... 30 Waitoa River – Procedures ...... 31 Background Information ...... 31 Flood Procedures (Waitoa River at Waharoa) ...... 32 Flood Procedures (Waitoa River at Mellon Rd) ...... 33 Ringing List No.1 ...... 34 Waitoa River at Mellon Rd Return Periods ...... 34 Waitoa River at Paeroa-Tahuna Road Return Periods...... 34 Piako River - Procedures ...... 35 Background Information ...... 35 Flood Procedures (Piako River at Kiwitahi)...... 36 Flood Procedures (Piako River at Paeroa-Tahuna Rd)...... 37 Flood Procedures (Piako River at Maukoro Landing Rd)...... 38 Ringing List No. 1: P-T Road...... 39 Ringing List No. 2: Maukoro Landing...... 39 Ringing List No. 3 ...... 39 Ringing List No. 4 ...... 40
Flood Warning Procedures Manual 2003 Page ix Piako River at Paeroa-Tahuna Rd Return Periods ...... 40 Waikato River - Procedures ...... 41 Background Information...... 41 Why provide Flood Warnings?...... 41 Upper Waikato River ...... 42 Management with Respect to the Waikato Hydro-Electric System...... 42 Lower Waikato River...... 42 Flood Procedures (Waikato River at Hamilton)...... 44 Waikato River at Hamilton: Return Periods...... 45 Waipa River – Procedures ...... 46 Background Information...... 46 Why provide Flood Warnings?...... 46 Flood Procedures (Mangaokewa River at Te Kuiti) ...... 47 Mangaokewa River at Te Kuiti: Return Periods ...... 48 Flood Procedures (Waipa River at Otewa)...... 48 Flood Procedures (Waipa River at SH31 Bridge Otorohanga)...... 48 Flood Procedures (Puniu River at Barton’s Corner Rd Bridge) ...... 48 Flood Procedures (Waipa River at SH23 Bridge Whatawhata)...... 49 Waipa River at Whatawhata: Return Periods...... 50 Waikato River below Waipa River – Procedures...... 51 Flood Procedures (Waikato River at Ngaruawahia)...... 51 Waikato River at Ngaruawahia: Return Periods ...... 52 Flood Procedures (Waikato River at Huntly Power Station)...... 53 Waikato River at Huntly – Tainui Bridge: Return Periods...... 54 Flood Procedures (Waikato River at Rangiriri)...... 55 Waikato River at Rangiriri: Return Periods ...... 56 Flood Procedures (Waikato River at Whangamarino Control Structure)...... 56 Flood Procedures (Waikato River at Mercer) ...... 59 Ringing List No.1...... 60 Waikato River at Whangamarino Control Structure: Return Periods...... 61 Flood Procedures (Whangamarino River at Ropeway)...... 61 Flood Procedures (Community Gate Operation & Setting)...... 62 Lake Waikare Typical Values and Control Setting...... 63 Mangawara River - Procedures ...... 65 Background Information...... 65 Statistics of the Mangawara Scheme ...... 65 Why provide Flood Warnings?...... 66 Flood Procedures (Mangawara River at Jefferis)...... 66 Mangawara River at Jefferis: Return Periods...... 67 Mangatangi River - Procedures ...... 68 Background Information...... 68 Flood Procedures (Mangatangi River at SH2) ...... 72 Mangatangi River at SH2: Return Periods ...... 72 Mangatawhiri Catchment – Background Information...... 73 Background Information...... 82 Flood Procedures (Tongariro River at Poutu Intake)...... 85 Tauranga-Taupo River – Procedures...... 87 Background Information...... 87 Why provide Flood Warnings?...... 87 Flood Procedures (Tauranga-Taupo at Te Kono)...... 88 Contact Numbers...... 89 Return periods as derived by Tonkin and Taylor...... 90 Awakino River - Procedures...... 91 Background Information...... 91 Why provide Flood Warnings?...... 91 Flood Procedures (Awakino River at SH3)...... 91 Other Contact Details...... 93 Awakino River at SH3: Return Periods...... 93 Coastal Flooding - Procedures...... 94 Firth of Thames Coastline...... 94 MetService Warnings for Abnormally High Sea Water ...... 94 Typical Storm Surge Indicators ...... 94 Alarm Settings and Promulgation...... 95 Contact Details ...... 95 Tidal Constituents and Definitions ...... 95
Page x Doc # 761111 Tararu Storm Surge Forecasting Model...... 96 Waikato River at Hoods Landing (Tide / River Gauge)...... 98 Brian’s Weather Links:...... 98 MetConnect:...... 98 Whitianga Harbour Tide Gauge ...... 98 Appendix B ...... 99 HydroTel Operation Modes...... 99 Day/Night/Alert Modes ...... 99 Day Mode ...... 99 Night Mode...... 99 Alert Mode...... 99 Summary of Actions:...... 99 Appendix C ...... 101 Telemetry System (HydroTelTM) Configurations...... 101 Polling Times ...... 101 Alarm Promulgation ...... 101 Polling Times Under Flood Conditions ...... 101 Special Polling Times for ‘Flashy and Key Indicator Sites’...... 101 Special 0832 and Environment Waikato’s Website Updates...... 101 Appendix D ...... 102 Media Releases...... 102 First Media Release...... 102 Purpose ...... 102 Corporate Media Liaison Officer – Contact Details: ...... 102 Appendix E ...... 103 Flood Operations Centre (FOC)...... 103 Activation based on Flood Conditions...... 103 Purpose ...... 103 Procedures ...... 103 Activating the Flood Operations Centre ...... 103 De-Activating the Flood Operations Centre ...... 103 Appendix F ...... 104 Antecedent Precipitation Index ...... 104 Flood Risk Index ...... 106 Appendix G...... 108 Metservice Information...... 108 Severe Weather Warnings (SWW)...... 108 MetService Contact Details...... 108 MetConnect ...... 109 Appendix H ...... 110 0832 River Level & Rainfall Infolines ...... 110 Appendix I...... 111 Flood Logs...... 111 Appendix J...... 113 Post-Event Review and Operational Improvements...... 113 Criteria: ...... 113 Appendix K ...... 114 SYSTEM SUPPORT...... 114 Appendix L...... 115 Performance Measures For Flood Warning ...... 115 Target Outcomes ...... 115 Customer Focus ...... 115 Appendix M...... 116 Supporting Information...... 116 Contents: ...... 116 Bibliography...... 117 General...... 117 Taupo Basin ...... 117 Western Seaboard...... 117 Waipa ...... 117 Lower Waikato...... 118 Piako-Waitoa ...... 118 Waihou-Ohinemuri...... 118 Kauaeranga-Coromandel...... 119
Flood Warning Procedures Manual 2003 Page xi
Page xii Doc # 761111 The Purpose and Objectives of Flood Warning The purpose of Environment Waikato’s flood warning service is to reduce the impacts of flooding, through the provision of information about the likelihood of a flood event occurring. This information allows customers to make informed decisions about how they can lessen or avoid flood damage (and other impacts) to their property as it provides them a greater certainty about the likelihood, location and magnitude of potential or actual river and coastal flooding. It also provides security to the community in the knowledge that the potential for flooding is being monitored and that they will be given adequate early warning.
The service provides broad coverage across the region. The focus is on the major river systems, where the potential impacts are large, and significant portions of the community in the region can be affected. The service is also able to provide timely flood warnings, allowing subsequent effective response to minimise damage within those systems.
It should be stressed that flood warning is only one component of reducing flood damage. Effective catchment land use management practices, floodplain management and land use control, building controls, flood protection systems, and ultimately Civil Defence Response are all proven methods for reducing flood damage.
Objectives:
1. Reduce the impacts of flooding
2. Allow customers to make informed decisions
3. Provide security to communities in the knowledge that the potential for flooding is being monitored
4. Issue warnings in advance of anticipated events, provide real time data for flood forecasters
5. Provide a robust, reliable, highly beneficial service
6. Maintain specialised staff
7. Have the most well-respected and comprehensive flood warning system in New Zealand
Flood Warning Procedures Manual 2003 Page 1 Customers Key customers of the flood warning service are: a) Territorial Local Authority Civil Defence/Emergency Management b) Householders and property owners (urban and rural) c) Communication and Transportation Network Users, and d) Flood Defence, Land Drainage, and Communication and Transportation Network Managers (internal and external).
Customers consider reliable, early warnings to be very important. Some customers have there own performance measures, which are time-bound, especially for services such as road maintenance that are contracted out. Dissemination therefore needs to start early so that customers can make arrangements for response actions and so that communications systems can be tested and refined if necessary during the development of a potential flood.
More detailed information on customers and how they use flood warnings is detailed in ‘The Review of Environment Waikato’s Flood Warning Service’ (Palmer, 1996).
Page 2 Doc # 761111 Content of Flood Warnings The flood warning service provides the following information to customers:
A) MetService Severe Weather Warnings (Appendix F)
B) Daily/weekly weather forecasts (MetConnect, Appendix F)
C) Alert Levels for each of the eight major catchments (see Table 1)
D) 24 hr access to River Level/Rainfall Information via the 0832 Infoline Service (Appendix G)
E) Measured rainfall and river levels in each of these catchments, and
F) Predictions of the likely change in river level at indicator sites within each catchment over a six hour forecast period.
Caution: Please note that these alert levels have no direct correlation with the Alarm Levels (Alert Levels are generally used only for media and external customers).
Flood Warning Procedures Manual 2003 Page 3
Regional F.W. General Public
By General Broadcast
Data/Information Services Regional F.W. EMT Flood Warning - Met Service Major organisations Service - Hydrometric network By Direct (incl EW Asset Managers) - MRP Notification - Others
Site Specific F.W. Parties with Agreed By Direct Services Delivery Notification Contracts
Figure 2: Dissemination of Flood Warnings
The flood warning service will advise on general potential impacts and appropriate response actions. However, specific response actions, such as self-evacuation and stock movements, are the responsibility of the affected individual or organisation.
Page 4 Doc # 761111 The Flood Warning Team Core members of Environment Waikato’s flood warning team are: a) Level 1 Emergency Management Officer (EMO 1) b) Level 2 Emergency Management Officer (EMO 2) c) Hazard Liaison Officer (HLO) - Paeroa d) Hazard Liaison Officer (HLO) - Taupo e) Telemetry System Supervisor f) Programme Manager Natural Hazards/Emergency Management g) Natural Hazards and River Services Officer h) Media Liaison Officer i) Environment Freephonist
The Emergency Management Duty Roster rotates trained personnel on a weekly duty basis to provide a continual 24 hour contact for customers. It is updated bi- monthly and is available electronically to all internal staff. It is also sent out to district councils, Mighty River Power (MRP), MetService, and the Ministry of Civil Defence. Relevant contact details are attached to the roster for staff convenience.
Contact details are available in the Duty Roster (Refer Appendix J for access details). The EMO cellphone is available for discretionary use by the Level 1 and Level 2 EMO’s in situations where they do not have access to a telephone and where they may have to action alarms.
Flood Warning Procedures Manual 2003 Page 5 Management Procedures The transition from “normal” meteorological and hydrological conditions to a flood should be reflected in the manner in which the flood warning team operate. The EMO 1 should become increasingly pro-active in obtaining and disseminating information as the flood situation develops. There should be a shift from monitoring the situation part- time to one of managing it full-time when key alarm levels are reached/exceeded.
To facilitate this, six flood alert levels have been defined (Table 1).
1. Level One Emergency Management Duty Officers are required (at all times) to carry with them the Level 1 pager, cellphone, and a copy of this manual during their week of duty. 2. Level Two Emergency Management Duty Officers are required to carry a pager, a copy of this manual during their week of duty.
This equipment should be maintained in operating condition. Procedures and staffing requirements at each alert level follow.
[Please refer to Appendix A for catchment-specific procedures]
Page 6 Doc # 761111 Civil Defence Warning System Test Messages Civil Defence warning system test messages are generally carried out every three months by the Ministry of Civil Defence and Emergency Management as part of their preparedness for a real life national emergency. The messages are issued via fax, email, and/or text message.
Until recently, these tests were only conducted during normal office hours but a recent initiative has meant that these tests are now conducted during after-hours. The Level 1 EMO cellphone (and pager) number will therefore be the nominated contact for the after-hours test. Test messages issued during normal office hours will be actioned by the Regional Civil Defence Officer (as per the status quo).
Please contact Adam Munro or Brendan Morris if you require information.
Procedures
Upon receipt of a Civil Defence warning test message during after-hours, the Level 1 EMO (with assistance from the Level 2 EMO) is to carry out the following procedures. The contact details of each of the territorial authorities involved are also provided.
CIVIL DEFENCE WARNING SYSTEM – TEST MESSAGE
This is a test to exercise the passage of a civil defence warning message as required under Part Three, National Civil Defence Plan. The message is being sent by fax and email, and supported by a text notification. Please action as detailed below.
A Territorial Authorities: 1. Confirm receipt of test message to your Regional Council (within 30 minutes).
B Regional Councils: 1. Contact Territorial Authorities and check that test message was received (where TA’s do not confirm receipt within 30 minutes). 2. Contact the MCDEM Emergency Management Advisor (EMA) for your Region within one hour (use the EMA’s cell phone no for after hours) or if unavailable, contact the National Duty Officer at 04-473 0021 to advise receipt of the test message by all territorial authorities.
EMA phone no’s are: John Titmus (Upper NI): 09 262 7830 (office); 027 4489 374 (cell)
C MCDEM EMA’s: 1. Check that the test message has been received by Regional Councils and if not, convey message. 2. Confirm receipt of test message by Regions to the National Duty Officer at 04- 473 0021 / 027 442 1236 or email [email protected]
(Police Communications Centres are requesting Police Districts to liaise with local civil defence organisations to check that test message has been received).
Flood Warning Procedures Manual 2003 Page 7
Territorial Authorities – Contact Information Organisation Phone (work) Afterhours / Fax Contact Name Mobile
District Councils Thames- (07) 868 9586 (07) 868 9962 (07) 868 9586 Ron White Coromandel (07) 868 6025 0274 981 871 Waikato (07) 824 8633 (07) 854 6565 (07) 824 8091 Bill Radford 025 944 511 Waipa (07) 871 7133 (07) 871 8712 (07) 871 4061 Chuck Davis 025 394 581 Waitomo (07) 878 8801 (07) 878 6006 (07) 878 7771 John Moran 029 878 6006 Taupo (07) 376 0803 or 0274 930 557 (07) 376 0619 Martin Sears / (07) 376 0850 Grant Singer South Waikato (07) 886 1777 (07) 886 1710 (07) 886 1777 Barrie Herlihy 025 950 973 Otorohanga (07) 873 8199 (07) 871 9334 (07) 873 8813 David Hall
Hamilton 838 6595 (Ray) 838 6699 838 6599 Ray Pooley / 846 1916 (Graeme) 021 961 749 Graeme Cleaver Ministry for Civil Defence / Emergency Management Auckland (09) 262 7830 (09) 576 7478 as above John Titmus 027 448 9374 026 111 964
Page 8 Doc # 761111
Appendix A
Action Plans - All Catchments
Ohinemuri River - Procedures
Background Information The Ohinemuri River is the major tributary of the Waihou River, with its headwaters located in the hills northeast of Waihi. It has two substantial tributaries entering between Waihi and Paeroa. These are the Waitekauri located north of Waikino, and the Waitawheta located south of the Karangahake recorder site. At the confluence with the Waihou, the Ohinemuri has a substantially greater peak flood flow than the Waihou River itself. This is due to its geographical location (it is susceptible to severe weather patterns) and the very steep nature of its catchment (the river actually represents the division between the Coromandel and Kaimai Ranges). The river flows westwards through the Karangahake Gorge via the Waihi basin, exiting the ranges near Paeroa on the low-lying flatlands of the Hauraki Plains.
Paeroa is therefore most at risk from flood events originating on the Ohinemuri River.
As a consequence, the river (under the Waihou Valley Scheme) has been stopbanked over its lower 14.2 km, and is therefore reasonably entrenched over the upper 12km of this reach. In general, the river is relatively steep and flood velocities are therefore significantly higher than for the Waihou River. The floodway and stopbank system is vital for Paeroa. Throughout the lower reach, major floodgate outlets are constructed and are complemented by major flood pumps to provide drainage and dewatering facilities to, in general, cope with 10 year flood events in the rural areas and 50 year flood events in Paeroa.
Further upstream, the channel is generally well entrenched, with the Karangahake Gorge being the major feature. SH2 is vulnerable to closure in events greater than the mean annual flood (or 16.15 m at the Karangahake Recorder). Scenarios of the extent of flooding due to stopbank breaches at key points are being developed.
SH 26 will be closed south of Criterion Bridge due to the placement of stoplogs when flood levels predicted exceed 8.4 m at the Bridge. This corresponds to a level at Karangahake of 16.5 m, which is only just greater than a mean annual event.
Further information on this river system can be found in the Waihou Valley Scheme Asset Management Plan 1997. Further investigations of this system are currently being undertaken through a UniTech Masters Student project.
Climate: Warm and wet. Average annual rainfall is near 2700 mm/y in the north, closer to 1500 mm/y in the south. Catchment area: 287 km2. Mean flow: 12 m3/s. Minimum flow: 1.1 m3/s. Maximum flood: 1047 m3/s.
Water clarity and monthly mean river flow. Motorists travelling from Waihi to Paeroa are treated to views of sheer bluffs, tumbling rapids with boulders the size of cars, and serene pools as the Ohinemuri River winds through the spectacular Karangahake Gorge. During floods the raging river is an adrenalin thrill for kayakers. On sunny weekends families stroll along the banks, soaking up the river’s beauty and the many relics of gold processing plants. But the Ohinemuri has a checkered history as one of the most abused rivers in New Zealand.
Flood Warning Procedures Manual 2003 Page 9 The river today. Before European settlement the river drained bush and scrub in the Waihi basin and peat swamps and kahikatea forest in the lower catchment above the confluence with the Waihou River which flows to the Firth of Thames. The Ngati Koi had settlements on the natural levees along the lower river, and eel and whitebait fisheries contributed to their food. European impacts began with forest clearance and wetland drainage for farming from about 1840. Extensive exploitation of the upper catchment began in 1875 when the area was opened up for gold mining. In 1895 the river was declared a sludge channel by the Government, and processed ore from stamping batteries was dumped into the river until 1952 when gold mining first ended at Waihi. The dumping made the river very turbid and silted up the lower reaches, and the sediment and heavy metals would have severely degraded fisheries and other aquatic life. Today the river is much improved, but still under stress. The modern mining operations have minimal impact on the river, but leachate legacies from old mines and associated mullock piles and tailings raise heavy-metal levels above guidelines at a few sites, and nutrients from agricultural runoff and treated sewage discharged from Waihi support abundant algal growth. Macroinvertebrate Community Index values have been consistently low since monitoring began in 1989 at the National River Water Quality Network monitoring site at Karangahake. As we enter the 21st century, the worst toxic pollution of the resource-exploitation era has been solved, but the challenges of dealing with nutrients discharged from our settlements and insidious diffuse pollution from agriculture remain. Ohinemuri The full name is Te Waitangi-o-Hinemuri: literally "the weeping water of Hinemuri, the youngest daughter". In Maori legend the river and floodplain were formed by the tears of Hinemuri. She was the youngest daughter of the Hauraki chief who turned away her many suitors because her older sisters remained unwed until finally the suitors fell away and she was left alone and disconsolate. Her copious tears formed the river and floodplain.
Page 10 Doc # 761111
Why provide Flood Warnings? Environment Waikato provides flood warnings for this river system because:
1. Its “track record” suggests that it floods frequently - potentially threatening Paeroa and the surrounding areas in significant events.
2. Its vulnerability to “flash” flooding (due to its geographical location and steep upper catchment) makes the time for any necessary response very short. Potential impacts include the closure of State Highway 2 through the gorge (main access route between Tauranga and Auckland) and the isolation of small settlements such as Waikino.
3. Some lower river flats are grazed and farmers need timely warnings to move stock.
4. It provides vital information and assurance for the local Civil Defence organisation during major events.
Telemetered flood warning stations related to this river system are:
Rainfall Waitekauri Catchment @ Golden Cross (Rainfall Intensity Alarm = 60mm in 3 hours)
API Catchment Groupings of API Values (mm) Low Moderate High Extreme Waihou- Ohinemuri 0-100 100-200 200-300 300+
Water Level Ohinemuri River @ Karangahake
Flood Warning Procedures Manual 2003 Page 11 Flood Procedures (Ohinemuri River at Karangahake) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP < mean Fully Activate HydroTel or Use Day, Night & Alert Modes annual Environment Waikato WebSite River 14.0 Levels & Rainfall Alarm message sent to L1 EMO Monitor Rainfall at Golden Cross to EMO 1 & 2 – Pager determine extent of the storm duration and intensity) EMgt Officers – Email Monitor water level @ Karangahake Maintain flood log (refer Appendix I to Thames Civil Defence – print off copies - File to: 30 08 05). Pager, Email & Fax Record all comments and times various people are contacted/informed Hauraki DC – Email & Fax Advise Civil Defence (Thames) NIWA-Hamilton – Email
Paeroa Office – Fax
Jianlibao – Fax & Email Inform: (to alert for Ohinemuri WVS Programme Manager Flood & close their (Owen Passau (025) 836 045 or a/h (07) floodgate as level reaches 884 8855) 14.8m) Works Supervisor Paeroa / HLO (Kevin Campbell 025 972 736 or a/h Ph 07 862 7608) – advise if 16.5m is likely at Karangahake then 8.4m at Criterion Bridge is likely & stop logs will need to be erected. Ian Sara (025) 972 698 or a/h (07) 867 6836
Advise rate of rise and if 8.4 m @ Cri Bridge is likely (16.5 m @ Karangahake) then instruct insertion of stop logs
External Notifications: • Jason Schirmak, Opus, Ph 025 785 989 or (07) 862 7732 • inform of situation (present level) • state that at 15.8m, parts of SH2 through the gorge begin to flood • advise that next contact time will be if level 15.2m looks imminent Ringing Lists Level 1 EMO is to ring people on Ringing List No.1 on Page 22. Once all notified, advise the Works Supervisor Paeroa (Kevin Campbell).
Page 12 Doc # 761111
Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP < mean HydroTel Activated Fulltime Day, Night & Alert Modes annual L1 EMO 15.0 m Notify WVS Programme Manager of Alarm message sent to above proceedings Notify Kevin Campbell (Paeroa) EMO 1 & 2 – Pager Notify Ron White, Civil Defence: Work Ph (07) 868 9586 EMgt Officers – Email Mobile 0274 981 871 Pager 026 246 2655 Thames Civil Defence – Pager, Email & Fax
Hauraki DC – Email & Fax Notify Ian McLeod @ Hauraki DC
Ph (07) 862 8609 NIWA-Hamilton – Email Direct Kevin Campbell to organise 30
min readings from Criterion Bridge (> Paeroa Office - Fax freq. if needed)
Re-contact Fulton Hogan Hamilton.
Tawa Goldsmith Ph 025 858 427,
Jason Schirmack, Opus, Ph 025 785
989 or 07 862 7732
Advise that stage 15.5 m looks
imminent and 15.8 m likely (according
to hydrograph)
Patrol Areas < mean HydroTel Activated Fulltime annual HLO Paeroa 16.0 m Re-contact Ian McLeod @ Hauraki DC. Ph (07) 862 8609 Inform that a level of 16.0 m @ Karangahake is possible Parts of SH2 are possibly flooded Indicates likely level @ Paeroa of 7.0 - 7.5 m (depending on d/stm conditions) Use readings from Criterion Bridge gaugeboard and Puke Bridge telemetry to extrapolate likely flood peak Pereniki Spillway operating level is 7.45 m at top end. This gauge should now be monitored regularly by field staff (in Tandem with Criterion Bridge)
Flood Warning Procedures Manual 2003 Page 13 > mean Based on above, a prediction should Day, Night & Alert Modes annual be made of the Karangahake level, 16.5 m which should equate to a Criterion Alarm message sent to Bridge level of 8.4 m Contact Kevin Campbell & advise that EMO 1 & 2 – Pager this is the recommended level for the stop logs on the left bank to be EMgt Officers – Email installed (likely 8.4m @ Criterion Bridge) Thames Civil Defence – At this stage, the freeboard below the soffit Pager, Email & Fax on Criterion Bridge is ~ 0.4 m. Kevin Campbell is to contact (for Hauraki DC – Email & Fax confirmation) Ron White, Civil Defence Thames. Ph 07 868 9586 or NIWA-Hamilton – Email 0274 981 871 Paeroa Office - Fax
ADVISE that SH26 is closing at Criterion Bridge Note: Time of travel from Karangahake Recorder to Paeroa at these stages is approximately 1 hour. 5 years Level 1 EMO is to update predicted (20% levels for Paeroa / Puke Bridge from 17.0 m AEP) data and hydrograph plots. Advise Owen Passau and Kevin Campbell When a level of 9.0 m at Criterion Bridge can be confidently predicted, notify Owen Passau and Kevin Campbell - ADVISE the following
Paeroa: Two sets of stoplogs exist on the RB area, one adjacent to the NZCDC Factory on Thorp St, the other at Criterion Bridge. These are to be installed when the predicted level at Criterion Bridge is 9.0 m or above.
Floodway Capacities Design Flood Level at Criterion Bridge = 9.21 m RL (+0.9 m freeboard) = 10.11 m Design Flood Level at Railbridge site (which has since been demolished) = 8.54 m (+ 0.9 m freeboard) = 9.44 m Information on the Waihou River above and below Puke Bridge should now be collected in the Netherton, Hikutaia Cut, Tirohia, and Cadman Road areas. If the Waihou is high prior to the flood, there will be backwater effects raising the level in the Tirohia area, and increasing the levels towards Netherton
Page 14 Doc # 761111
Ringing List No.1
Contact Number Area Affected Karl Rasmussen or 07 862 8876 Fax, 07 862 8214 Mill Rd / Gerrands Rd Paul Rasmussen 07 862 7189 Fax; 07 862 8214 Mill Rd / Gerrands Rd WR Tye or 07 862 4914 SH2 [email protected] Mrs RE Tye 07 862 8866 SH2 Harvey Reid 07 862 7187, 07 8627127 Puke Berms [email protected] (away 1 March – 7 July 04)
Bill Tissingh (Farm Manager) 07 862 8716, 021 862 871 Daniel Murdoch (Sharemilker) 07 8624910 Netherton Bend
Graham Morrison 07 862 4726 Fax: 07 862 4947 James Newton 07 862 4811 Netherton Bend (for Graham Morrison being overseas) Dave & Karen Leigh or 07 549 2811 Puke / Maritime Park Fax: 07 549 1135 Toni & Wayne Reeve 07 862 6363 Puke / Maritime Park Brett Johansen or 07- 8626030 or 0272880301 Pereniki Bend Mill Rd Berms Mike Peters 07 - 8264281 or 0274758984 Pereniki Bend 07 – 8264381 (FAX) Mill Rd Berms
Contact the Works Supervisor Paeroa (Kevin Campbell), and advise that all the above have been notified. Specified Levels
Approximate Annual Highest Recorded Levels
Karangahake 15.00 m 18.66 m
Paeroa 7.50 m 9.60 m (Criterion Bridge)
Puke Bridge 2.75 m 5.75 m
Tirohia 5.15 m 7.57 m
Ohinemuri River at Karangahake Return Periods
Return Period (yrs) 2.33 5 10 20 50 100 Gauge Height (m) 16.15 16.95 17.50 17.90 18.40 18.65 Discharge (m3/s-1) 490 650 770 870 970 1040
Flood Warning Procedures Manual 2003 Page 15 Kauaeranga River – Procedures
Background Information The Kauaeranga River, while not strictly part of the Waihou River system (as it flows directly into the Firth of Thames), is the third major river system within the Waihou Valley Scheme. The steep catchments in this section of the Coromandel Ranges produce very high peak flood flows, with the 1% AEP (100 year return period) flood event being very similar to that of the Ohinemuri River.
The headwaters are located to the north of Thames up the Kauaeranga Valley. The river flows southwards exiting the Coromandel Ranges on the southern fringes of Thames township. It has three main tributaries on the middle to lower reaches, these being the Mangarehu Stream, Piraunui Stream and the Hihi Stream. The individual contribution of these streams to the overall Kauaeranga River flood peak during heavy rain is not considered significant. On the left bank, an overflow spillway is located immediately upstream of SH25, with the floodway extending across the state highway through Rhodes Park. The spillway is designed to operate in events greater than the 20% AEP (5 year return period) flood.
Throughout the lower reach, major floodgate outlets are constructed and are complemented by flood pumps to provide drainage and dewatering facilities to, in general, cope with the 50% AEP (2 year return period) flood. Flood flows can carry significant debris. Further information on this river system can be found in the Waihou Valley Scheme Asset Management Plan 1997.
The lower reaches of the Kauaeranga River are tidal, to calculate the high and low tides this Niwa site can be used, http://www.niwa.co.nz/services/tides.
Interesting facts on rainfall at Pinnacles site
Continuous records began 1991 Highest 24 hour rainfall total 426 mm on 29th and 30th December 1996 Maximum recorded annual rainfall total 4668 mm in 1998 Mean annual rainfall total 3800 mm Minimum recorded annual rainfall total 2930 mm in 1994 Why provide Flood Warnings? Environment Waikato provides flood warnings for this river system because:
1. Areas outside the scheme area are becoming further developed. This includes access roads up the valley, schools, houses, infrastructure, and property which are either regularly inundated or at medium to serious risk. 2. Its “track record” suggests that it floods frequently – potentially threatening Thames and the adjacent areas in significant events. 3. Its vulnerability to “flash” flooding (due to its geographical location and steep upper catchment) makes the time for any necessary response very short. Potential impacts include the closure of SH25 into Thames (main access route) and the isolation of the rural community located in the Kauaeranga Valley. 4. Some upper and lower river flats are grazed and farmers need timely warnings to move stock. 5. It provides vital information and assurance for the local Civil Defence organisation during major events.
Page 16 Doc # 761111
Telemetered flood warning stations related to this river system are:
Rainfall: Kauaeranga Catchment @ Pinnacles (Rainfall Intensity Alarm set at 60mm in 3 hrs)
API Catchment Groupings of API Values (mm) Low Moderate High Extreme Kauaeranga -Coromandel 0-20 20-40 40-60 60+
Water Level: Kauaeranga River @ Smiths
Flood Procedures (Kauaeranga River at Smiths) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP Fully Activate HydroTel or Use Day, Night & Alert Modes Environment Waikato WebSite < mean River Levels & Rainfall Alarm message sent to annual L1 EMO 7.7 m EMO 1 & 2 – Pager
Monitor rainfall at Pinnacles Monitor water level at Smiths EMgt Officers – Email
Flood Warning Procedures Manual 2003 Page 17 Fully Activate HydroTel L1 EMO Thames Civil Defence – < mean Continue to… Pager, Email & Fax annual Monitor rainfall at Pinnacles 8.5 m to determine extent of the NIWA-Hamilton - Email storm duration and intensity Paeroa Office – Fax Monitor water level at Smiths
Notify: Ian Sara (Works Supervisor Kerepehi). Ph 07 867 6836 (a/h) or cell (025) 972 698
HLO Paeroa (Kevin Campbell) Ph 07 862 7608 (a/h) or Cell phone 025 972 736. Advise that Kauaeranga River Flood events often lead to Ohinemuri River flood events
Ph 07 862 7608 a/h or cell (025) 972 736
Owen Passau (WVS Programme Manager) Ph 07 884 8855 (a/h) or cell (025) 294 5808
Ron White (Area CD Officer) Ph 07 868 9962 or cell (0274) 981 871
There will usually be a minimum time of 20 minutes before a level of 8.5 m is reached.
Inform them of rate of rise over last half hour and anything else relevant (e.g. the level at Karangahake)
As level increases to 9.0 m, check HydroTel regularly
Page 18 Doc # 761111
Fully Activate HydroTel Day, Night & Alert Modes < mean 9.0 m L1 EMO Alarm message sent to annual
Contact should be made EMO 1 & 2 – Pager again with: Ron White CD Officer (TCDC): Ph 07 868 EMgt Officers – Email 9962 or cell (0274) 981 871 Thames Civil Defence – Pager, Email & Fax
Notify: NIWA-Hamilton – Email
Thames Airfield: Ph 07 868 Paeroa Office - Fax 6445 or Ian Hague: Ph 07 868 8898 (ring only if before 1800 hrs as machinery etc needs shifting) Montgomery Watson, Thames Ph (07) 868 5656 McBreen Jenkins BoP Ph (07) 863 7548
Water begins to lap Kauaeranga Valley Road at 9.3 m. If there are any problems occurring with the Smiths recorder, efforts should be made (if possible) to have someone posted to read the gaugeboard at Smiths and transmit the readings via Cell Phone or R/T
Flood Warning Procedures Manual 2003 Page 19 < mean Fully Activate HydroTel annual L1 EMO 9.8 m Contact Programme Manager (Owen Passau): Ph 07 884 8855 or 025 294 5808 Works Supervisor Kerepehi (Ian Sara) Ph 07 867 6836 or 025 972 698. Depending on the tide, SH25 from Parawai to Thames will flood to a depth whereby vehicle access may be 4x4 drive only. Inform Civil Defence that the road is likely to be flooded when a confident prediction can be made from Smiths reaching RL 10.5 m. SH25, Airport and adjacent areas are protected by stopbanking and spillways should overtop when Smiths reaches this level.
< 5 years Monitor Smiths level or Day, Night & Alert Modes Kauaeranga River Bridge 10.5 m (20% AEP) against the overflow level at Alarm message sent to the road bridge. Check Thames Tide recorder for tide EMO 1 & 2 – Pager levels. EMgt Officers – Email Note: Time of travel from Smiths to Rolleston Street is Thames Civil Defence – approximately 1 hour Pager, Email & Fax
Re-contact Civil Defence NIWA-Hamilton – Email Officer at Thames. Ph 868 9586 or Mobile 0274 981 871 Paeroa Office - Fax
Floodway Capacities The final design standards for the Kauaeranga River works are as follows: a) To protect the areas of urban Thames, Barretts Road, Lowes Avenues and Totara Flats and Thames Airfield from the 1% AEP event (the level at Smiths Recorder of is yet to be defined), with a nominal freeboard of 0.9 m.
Page 20 Doc # 761111
b) To protect the above areas from flooding from the Firth of Thames to a level of RL 3.0 m, with a nominal freeboard allowance of 0.5 m. The only exception to this is the northern 150 m of the Toyota stopbank which has no freeboard.
Further information on this river system can be found in the Waihou Valley Scheme Asset Management Plan 1997. Kauaeranga at Smiths Return Periods Return Period (yrs) 2.33 5 10 20 50 100 Gauge Height (m) 9.90 10.55 11.05 11.50 12.00 n/a Discharge (m3/s-1) 490 665 800 940 1110 1240
Flood Warning Procedures Manual 2003 Page 21 Waihou River - Procedures
Background Information The Waihou River forms the major river system of the Thames Valley. It is a long narrow system located on the eastern side of the valley and drains the western slopes of the Coromandel, Kaimai, and Mamaku Ranges. The river flows directly into the Firth of Thames south of the Thames township. The lower reaches of the Waihou River are tidal, to calculate the high and low tides visit, http://www.niwa.co.nz/services/tides. At its headwaters in the Mamaku Ranges, the river is predominantly groundwater fed ensuring a steady supply of water year-round. The main tributaries to the Waihou River system are the Rapurapu, Waiomou, and the Oraka Streams in the upper reaches, and the Waiorongomai, Ohinemuri, and the Hikutaia Rivers located in the lower reaches.
Urban areas most at risk from a significant Waihou River flood event include (from south to north) Te Aroha, Paeroa, Turua, and Thames.
Due to the steep topography and the geographical location of the Kaimai and Coromandel Ranges, the Waihou River System is very susceptible to severe weather patterns originating from the northeast, and to a lesser extent from the SW. The steep western sides of the ranges also create/enhance orographic (localised) rainfall.
The Waihou Valley Scheme is comprehensive in the level of protection it provides. Flooding potential has been significantly reduced as a result of the scheme. For detailed scheme descriptions, refer to the Waihou Valley Scheme Asset Management Plan 1997.
Interesting facts on rainfall at Te Aroha Continuous records began 1986. (Daily rainfall data is available from 1907) Highest 24 hour rainfall total 184 mm on 7th and 8th September 1989 Maximum recorded annual rainfall total 1735 mm in 1989 Mean annual rainfall total 1236 mm Minimum recorded annual rainfall total 688 mm in 1993
Interesting facts on rainfall at Golden Cross (Waitekauri) Continuous records began 1990 Highest 24 hour rainfall total 372 mm on 29th and 30th December 1996 Maximum recorded annual rainfall total 3228 mm in 1996 Mean annual rainfall total 2569 mm Minimum recorded annual rainfall total 2015 mm in 1994
Why provide Flood Warnings? Environment Waikato provides flood warnings for this river system because:
1. Areas outside the scheme area are becoming further developed.
2. Its “track record” suggests that it is prone to severe floods (although the risk has been significantly reduced since the completion of the protection scheme) – potentially threatening the towns of Te Aroha, Paeroa, Thames, and the adjacent areas in significant events.
3. Potential impacts include the closure of many major roads, including SH26 (between Te Aroha and Paeroa) and the Te Aroha-Gordon Road. Isolation of the rural community would be the main effect if any of these roads are closed / inundated.
4. The river berms are grazed and farmers need timely warnings to move stock.
Page 22 Doc # 761111
5. It provides vital information and assurance for the local Civil Defence organisation during major events.
Telemetered flood warning stations related to this river system are:
Rainfall: Rapurapu Catchment @ Kaimai (Rainfall Intensity Alarm set at 60mm in 3 hours) Waitekauri Catchment @ Golden Cross (Rainfall Intensity Alarm set at 60mm in 3 hours) Waihou Catchment @ Te Aroha (Rainfall Intensity Alarm set at 30mm in 3 hours) Wharekawa Catchment @ Tairua Forest (Rainfall Intensity Alarm set at 60mm in 3 hours) Tamihana @ Matamata Airfield (Rainfall Intensity Alarm set at 30mm in 3 hours) Paeroa AWS (accessed from MetConnect to get last hour rainfall, wind speed, wind direction & barometric pressure readings)
API
Catchment Groupings of API Values (mm) Low Moderate High Extreme Waihou- Ohinemuri 0-100 100-200 200-300 300+
Water Level: Waihou River @ Okauia Waihou River @ Shaftesbury Waihou River @ Te Aroha Waihou River @ Tirohia Ohinemuri River @ Karangahake Waihou River @ Puke Bridge Waihou River @Peka Peka Methods for Predicting Levels Further modelling is required, but response staff in Paeroa & Te Aroha should be contacted for technical advice. Flood Procedures (Waihou River at Okauia) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP Routine monitoring Day, Night & Alert Mode 29.5 m Note: Alarm message sent to Armidale (Gordon Rd) floods when Okauia level is RL 30.0 m. EMO 1 & 2 – Pager
EMgt Officers – Email
Matamata-Piako DC – Fax
Te Aroha Depot – Fax
Paeroa Office - Fax
Flood Warning Procedures Manual 2003 Page 23 Flood Procedures (Waihou River at Shaftesbury) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP Routine monitoring. Day, Night & Alert Modes 16.0 m River at bank full stage. Alarm message sent to
Routine monitoring. EMO 1 & 2 – Pager
17.0 m Mace Rd floods when EMgt Officers – Email Shaftesbury level is RL 17.2m Matamata-Piako DC – Fax Routine monitoring. Te Aroha Depot – Fax 18.0 m Paeroa Office - Fax Routine monitoring.
19.0 m
Flood Procedures (Waihou River at Te Aroha) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP Routine Surveillance Day, Night & Alert Modes L1 EMO 9.3 m Alarm message sent to Note: EMO 1 & 2 – Pager Mace Rd floods when Te Aroha level is RL 9.8m. EMgt Officers – Email
Notify: Matamata-Piako DC – Fax
Te Aroha Depot – Fax Ringing list No.1 on Page 33 especially Craig Jamieson (formerly Malcolm property) Paeroa Office - Fax and John Moore (to be rung at any hour of the day or night) Fully Activate HydroTel Day, Night & Alert Modes L1 EMO 9.8 m Alarm message sent to Monitor rainfall at Kaimai Monitor water level at Okauia EMO 1 & 2 – Pager
Notify: EMgt Officers – Email Ringing List No 2 on Page 33 especially Craig Jamieson Matamata-Piako DC – Fax (formerly Malcolm property)(to be rung at any hour of the day or Te Aroha Depot – Fax night) Paeroa Office - Fax
Page 24 Doc # 761111
Fully Activate HydroTel L1 EMO Thames Civil Defence – 10.5 m Monitor rainfall at Kaimai to Pager, Fax & Email determine extent of the storm duration and intensity Hauraki DC – Fax & Email Monitor water levels at Okauia, Shaftesbury, and Te Aroha
Ringing List No. 3 on page 34
Notify:
Ron White (Area CD Officer) Ph: 07 868 9586 or 0274 981 871
Flood Warning Procedures Manual 2003 Page 25
Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP Fully Activate HydroTel Day, Night & Alert Modes L1 EMO 11.0 m Alarm message sent to Notify: Programme Manager WVS EMO 1 & 2 – Pager (Owen Passau) and advise the times various stages (9.5, EMgt Officers – Email 10.0, and 10.7 m) were reached, and the latest Matamata-Piako DC – Fax prediction and weather forecast (see MetConnect – Te Aroha Depot – Fax Page 94) Paeroa Works Supervisor Paeroa Office - Fax (Kevin Campbell) and advise that this is the level to check: Hauraki DC – Fax & Email Hikutaia Cut Spillway: which operated on 8/9/89 at a Puke Thames Civil Defence – Bridge level of 4.69 m (2 days Pager, Fax & Email ahead). Constantly monitor upstream and downstream levels using the telemetered readings from Okauia and Shaftesbury Rainfall data gathered should be passed on to the MetService to assist them in assessing the “local” situation Check hydrograph plots on the telemetry system to determine a possible peak Check previous profiles of hydrographs both at individual sites and longitudinally down the river to match the flood to historic event(s) Fully Activate HydroTel L1 EMO 11.4 m Notify: NZ Police (Ph 862 8744), Opus International (Ph 862 7732), and Kevin Campbell concerning flooding over Te Aroha-Paeroa Rd (SH26)
Page 26 Doc # 761111
Flood Procedures (Waihou River at Tirohia) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP L1 EMO Day, Night & Alert Modes Routine Monitoring 4.5 m Alarm message sent to
EMO 1 & 2 – Pager
L1 EMO EMgt Officers – Email Routine Monitoring 5.5 m Matamata-Piako DC – Fax L1 EMO Routine Monitoring, and Te Aroha Depot – Fax 6.0 m Monitor Tirohia closely and Paeroa Office - Fax predict a time for a level of 6.2 m. Time of travel between Hauraki DC – Fax & Email Tirohia and Te Aroha is approximately 19 hours. Thames Civil Defence – Pager, Fax & Email
Ringing List No. 1 Contact Work Phone Cell Phone A/Hrs Phone Area Affected Kevin Campbell 07 862 8376 025 972 736 07 862 7608 Roger Spooner 07 884 8101 0274 971 747 07 884 8603 Alan Sutton 07 884 8101 025 402 167 07 884 9746 Owen Passau 07 862 8376 025 294 1097 07 884 8855 John Moore 07 888 7938 025 975 611 Fax: 07 888 8268 Mangaiti Craig Jamieson 07 884 6088 Stirling St (formerly Malcolm property) Ted Williams 07 884 6747 Te Aroha u/s SH26 Bridge Peter Michels 0274 761 236 07 884 6884 “ Steven Davey 0274 824 597 07 884 9732 or [email protected] Fax: 07 884 9782 Ross Johnson 07 884 9714 Mangaiti Fax: Same as Phone # Greg Hemingway 07 884 7448 Mangaiti (Manager) Graham & Raewyn 07 884 9733 Strange Rd Davey Mark & Phillipa Davey 027 281 3621 07 884 9781 Strange Rd [email protected]
Flood Warning Procedures Manual 2003 Page 27 Ringing List No.2
Contact Work Cell Phone A/H Phone Area Phone Affected Kevin Campbell 07 862 8376 025 972 736 07 862 7608 Roger Spooner 07 884 8101 0274 971 747 07 884 8603 Alan Sutton 07 884 8101 025 402 167 07 884 9746 Owen Passau 07 862 8376 025 294 1097 07 884 8855 Ron White (Civil 07 868 9590 0274 981 871 Defence Officer) Matamata-Piako DC 07 884 0060 Mace Rd / (Tuk Sheehan) Armidale Rd Richmond Meats Work hrs only u/s SH26 07 884 9460 Bridge Peter Michels 0274 761 236 07 884 6884 “ Craig Jamieson 07 884 6088 Stirling St (formerly Malcolm property) John Moore 07 888 7938 025 975 611 Fax: 07 888 8268 Mangaiti Greg Hemmingway 07 884 7448 Mangaiti Colin Miller 07 884 9273 Stirling St Tim Rigter 07 884 9612 Wybom’s corner Brian Keightley 07 884 9737 Strange Rd Fax 07 8847030 Jim Shallue 021 884970 07 884 9703 Mangaiti Fax: 07 884 9703 mailto: [email protected] John and Linda Shallue 07 884 9706 or Waitoki (will be away 16 Dec 03 021 938 958 Please log to 6 Jan 04) 021 938 957 call if Fax: Same as Phone # manager rung Peter (Farm Manager) 07 8844449 Ari Rigter 07 884 9701 Waitoki George Avery 07 8628028 Waitoki Dave & Karen Leigh or 07 549 2811 Puke/Maritime Fax: 07 549 1135 Park Toni & Wayne Reeve 07 862 6363 Puke/Maritime Park
Page 28 Doc # 761111
Ringing List No.3 Contact Work Phone Cell Phone A/H Phone Area Affected Roger Spooner 07 884 8101 025 971 747 07 884 8603 Alan Sutton 07 884 8101 025 402 167 07 884 9746 Kevin Campbell 07 862 8376 025 972 736 07 862 7608 Ted Williams 07 884 6747 u/s SH26 Bridge Craig Jamieson 07 884 6088 Stirling St (formerly Malcolm property) John Moore 07 888 7938 025 975 611 Fax: 07 888 8268 Mangaiti Corrie Berkers 07 884 9724 Te Kawana Rd [email protected] Stephen Davey 07 884 9732 Bowlers Rd [email protected] Raewyn & Graham 07 884 9733 Strange Rd Davey Mark & Phillipa 027 281 3621 07 8849781 Strange Rd Davey [email protected] Greg Hemingway 07 884 7448 Mangaiti Greg Lochhead 025 281 0861 07 884 8318 Strange Rd Dean Andrews 021 923 507 07 884 5893 Elstow Mark Barker 021 149 3557 07 884 5844 (Sharemilker) John Shallue 07 884 9706 Waitoki David Grey 0274 840 940 07 868 1204 Waitoki/Rawhiti 0274 737 990 Rd Dave & Karen Leigh 07 549 2811 Puke/Maritime or Fax: 07 549 1135 Park Toni & Wayne Reeve 07 862 6363 Puke/Maritime Park John Hill 07 862 8622 Cadman Rd Brett Johansen or 07 – 8626030 07 862 6330 Pereniki/Mill or 0272880301 0274 244 4871 Rd berms Mike Peters 07 – 8264281 or 0274758984 07 – 8264381 (FAX)
Flood Warning Procedures Manual 2003 Page 29 Flood Procedures (Waihou River at Puke Bridge) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP Kevin Campbell to monitor levels Alert Mode Only downstream for possible Hikutaia 4.0 m Spillway Operation. Alarm message sent to
Hikutaia Cut Spillway: EMO 1 & 2 – Pager EMgt Officers – Email operated on 8/9/89 at a Puke Bridge Paeroa Office - Fax level of 4.69 m (2 days ahead). Hauraki DC – Fax & Email Thames Civil Defence – Pager, Fax & Email
Flood Procedures (Waihou River at Pekapeka) No alarms set as at 19/11/01. But Hikutaia Cut Spillway monitoring should be underway from Puke Bridge alarm. Approximate Annual Levels: Approximate Annual Highest Recorded Levels Okauia 31.00 m 33.13 m Shaftsbury 17.85 m 18.72 m Te Aroha 10.75 m 12.05 m Tirohia 5.15 m 7.57 m Puke Bridge 2.75 m 5.75 m Floodway Capacities Full descriptions of Design Specifications can be found in the Waihou Valley Scheme Asset Management Plan 1997 (Pages 3-10).
Since the majority of the scheme has been constructed to the 1% protection standard, the gauge height for the 100 year return event given in the above table (11.80 m at Te Aroha), can be regarded as the level when breaching of the stopbank is expected to occur in this section of the river (not including any freeboard).
Waihou River at Te Aroha – Return Periods (figures from 1998 rating review summary) Return Period (yrs) 2.33 5 10 20 50 100 Gauge Height (m) 10.6 11.0 11.25 11.45 11.70 11.85 Discharge (m3/s-1) 192 265 335 414 536 644
Refer also to document number 663306 by L Cooper, which revises the figure for the flood level at Te Aroha in a 1:100 year event. In this document a figure of 12.05m is given that allows 250mm for sediment loading.
Page 30 Doc # 761111
Waitoa River – Procedures
Background Information The Waitoa River is the major tributary of the Piako River (their confluence is approximately 5 km southeast of Patetonga on the Hauraki Plains). The headwaters are located near the small rural settlement of Buckland (south of Mt Te Tapui and east of Cambridge). The river meanders northwards flowing west of Matamata through low- lying, highly productive farmland.
The river channel of the Waitoa is deeply incised in most places, hence flooding isn’t a major concern on this river system. Any flooding that does occur is usually contained within its berms. However, some isolated “pockets” of ponding is possible on adjacent farmland.
Further information can be found in the Piako River Scheme Asset Management Plan 1997.
Interesting facts on rainfall at Wahoroa Continuous records began 1998 Highest 24 hour rainfall total 79 mm on 3rd and 4th December 1998 Maximum recorded annual rainfall total 1297 mm in 1998 Mean annual rainfall total 1141 mm Minimum recorded annual rainfall total 984 mm in 1999
Why provide Flood Warnings?
Environment Waikato provides flood warnings for this river system because:
1. When critical levels at some sites are exceeded, berm overflow can occur inundating adjacent farmland which is often used for grazing. Hence, farmers need timely warnings to shift stock. 2. It provides vital information for floodway managers to efficiently control floodpump/gate operations during times of high flows. 3. It provides data during times of low flow for major industries that utilise the river water for cooling, and for those farmers who extract the water for irrigation purposes (consents monitoring).
Telemetered flood warning stations related to this river system are:
Rainfall: Rapurapu Catchment @ Kaimai (indicative only) Piako Catchment @ Maukoro Landing (downstream of confluence) Tamihana @ Matamata Airfield
API:
Catchment Groupings of API Values (mm) Low Moderate High Extreme Piako-Waitoa 0-10 10-25 25-40 40+
Water Level: Waitoa River @ Waharoa Waitoa River @ Mellon Rd
Flood Warning Procedures Manual 2003 Page 31 Flood Procedures (Waitoa River at Waharoa) Alarm Return Actions Required by EMO/HLO HydroTel Status and Level Period Actions & AEP Routine Surveillance Day, Night & Alert Modes L1 EMO Alarm message sent to 47.0 m EMO 1 & 2 – Pager EM Officers – Email Te Aroha Depot – Fax Matamata-Piako DC – Fax Paeroa Office - Fax
Page 32 Doc # 761111
Flood Procedures (Waitoa River at Mellon Rd) Alarm Return Actions Required by EMO/HLO HydroTel Status and Level Period Actions & AEP Routine Surveillance Day, Night & Alert Modes L1 EMO 7.5 m Alarm message sent to
EMO 1 & 2 – Pager Fully Activate HydroTel L1 EMO EM Officers – Email 8.0 m Monitor the water level at the Waharoa recorder Te Aroha Depot – Fax Monitor Lower Waitoa using gauge board readings at Paeroa Office – Fax Waitoa P-T Road and North Road Matamata-Piako DC - Fax If level at Waitoa P-T Road is expected to exceed 4.3 m,
Notify: Ringing list No. 1 on Page 37 Waitoa P-T Road Level should get to 4.3 m if level at Mellon Road reaches 8.6 m At this stage, North Rd levels need to be monitored closely (staff gauge only). The levels at North Road will have a bearing on the levels at Maukoro Landing if Piako Peak has not reached Maukoro Landing. If the North Road level is likely to exceed 3.8 m, notify Brian Clarke Ph 07 887 5779. A level of 3.8 m is likely when the level at P-T Road is approximately 4.3 m. WVS Programme Manager (Owen Passau), and Te Aroha Works Supervisor (Roger Spooner) and HLO Paeroa (Kevin Campbell)
Alarm Return Actions Required by EMO/HLO HydroTel Status and Level Period Actions & AEP Fully Activate HydroTel Day, Night & Alert Modes L1 EMO 8.25 m Alarm message sent to As above EMO 1 & 2 – Pager Fully Activate HydroTel EMgt Officers – Email L1 EMO Te Aroha Depot – Fax 8.5 m Paeroa Office – Fax As above Matamata-Piako DC - Fax
Flood Warning Procedures Manual 2003 Page 33 Ringing List No.1
Contact Number Area Affected Leon Te Bogt 07 884 5752 P-T Road
McGregor 07 887 5762 P-T Road Fax: Same as phone # Maurice Chatfield 07 887 5838 North Rd Fax: 09 307 2074 Brian Clarke 07 887 5779 North Rd Fax: 07 887 5656 [email protected] Stuart Clarke 07 887 5588 North Rd 025 277 9000 or Use his parents fax # - B. Clarke. Peacock 07 887 5621 Confluence Fax: 07 887 5686
Waitoa River at Mellon Rd Return Periods Return Period (yrs) 2.33 5 10 20 50 100 Gauge Height (m) 8.25 8.40 8.45 - - - Discharge (m3/s-1) 42 54 64 73 86 95
Waitoa River at Paeroa-Tahuna Road Return Periods Return Periods (yrs) 2.33 5 10 50 100 Gauge Height (m) 3.5 3.9 4.05 4.35 4.5 Discharge (m3/s-1) 30 44 60 74 105
: there appears to be anomalies in the statistical values which suggest the return period estimates may be too high.
Page 34 Doc # 761111
Piako River - Procedures
Background Information The Piako River and its major tributary the Waitoa River have a combined catchment area of 1440 km2. The catchment is made up of a delta area from the Firth of Thames to the confluence with the Waitoa River, a middle area comprising the central Thames Valley extending south to the Matamata area, rolling downs in the vicinity of Morrinsville and a hilly area between Morrinsville and Cambridge.
The headwaters are located on the northeastern flanks of Mt Te Tapui (about 15 km south of Morrinsville). Large areas of land are only one or two metres above mean sea level, presenting significant drainage difficulties. The Piako River scheme is comprehensive in the level of protection it provides. Flood hazards have therefore been significantly reduced as a result of the scheme.
Much of the upper reaches of the river are deeply incised. Hence, there is very little threat of flooding to the adjacent farmland and communities.
The lower reaches of the Piako River are tidal, to calculate the high and low tides visit, http://www.niwa.co.nz/services/tides.
Further information can be found in the Piako River Scheme Asset Management Scheme 1997.
Interesting facts on rainfall at Maukoro Landing Continuous records began 1987 Highest 24 hour rainfall total 114 mm on 7th and 8th April 1995 Maximum recorded annual rainfall total 1494 mm in 1995 Mean annual rainfall total 1082 mm Minimum recorded annual rainfall total 802 mm in 1993
Why provide Flood Warnings?
Environment Waikato provides flood warnings for this river system because:
1. Areas outside the scheme area are becoming further developed. 2. Its “track record” suggests that it is prone to severe floods (although the risk has been significantly reduced since the completion of the protection scheme). 3. Potential impacts include the closure of many “link” roads and the isolation of rural communities. 4. Most, if not all of the river berms are grazed and farmers need timely warnings to move stock. 5. It provides vital information and assurance for the local Civil Defence organisation during major events. 6. It provides vital information for floodway managers to efficiently control floodpump/gate operations during times of high flows.
Flood Warning Procedures Manual 2003 Page 35
Telemetered flood warning stations related to this river system are:
Rainfall: Piako Catchment @ Maukoro Landing (Rainfall Intensity Alarm set at 3omm in 3 hours) Piako Catchment @ Maungakawa (Rainfall Intensity Alarm set at 30mm in 3 hours) Tamihana @ Matamata Airfield (Rainfall Intensity Alarm set at 30mm in 3 hours)
API:
Catchment Groupings of API Values (mm) Low Moderate High Extreme Piako-Waitoa 0-10 10-25 25-40 40+
Water Level: Waitoa @ Waharoa Waitoa River @ Mellon Rd Piako River @ Kiwitahi Piako River @ Paeroa-Tahuna Road Piako River @ Maukoro Landing Flood Procedures (Piako River at Kiwitahi) Alarm Return Actions Required by EMO/HLO HydroTel Status and Level Period Actions & AEP Routine Surveillance Day, Night & Alert Modes L1 EMO Alarm message sent to 2.5 m EMO 1 & 2 – Pager EMgt Officers – Email Te Aroha Depot – Fax Paeroa Office – Fax Matamata-Piako DC - Fax
Page 36 Doc # 761111
Flood Procedures (Piako River at Paeroa-Tahuna Rd) Alarm Return Actions Required by EMO/HLO HydroTel Status and Level Period Actions & AEP Fully Activate HydroTel Day, Night & Alert L1 EMO Modes 5.5 m Monitor rainfall at Maukoro Landing and Maungakawa to Alarm message sent to determine extent and intensity of storm EMO 1 & 2 – Pager Check status of Maukoro Landing and Kiwitahi telemetry EMgt Officers – Email sites If 6.0 m is expected at P-T Road, Te Aroha Depot – Fax
Notify: Paeroa Office – Fax Ringing List No. 1 on Page 41 WVS/PRS Programme Manager Matamata-Piako DC – (Owen Passau) to arrange check Fax of Whakahoro Rd, Drents, Russells, Steiners, North Rd Hauraki DC – Email & Floodgates, Drents pump and to Fax liaise with Land Drainage Programme Manager on Steiners and North Road pumps. Ian McLeod at Hauraki District Council: Ph 07 862 8609 or Mobile 025 969 558. A/h 07 889 3765 Fully Activate HydroTel L1 EMO 6.0 m As above, and Monitor the water level at the Kiwitahi recorder, & the sites on the Waitoa River. Fully Activate HydroTel L1 EMO 6.5 m As above Fully Activate HydroTel L1 EMO 7.0 m As above
Flood Warning Procedures Manual 2003 Page 37 Flood Procedures (Piako River at Maukoro Landing Rd) Alarm Return Actions Required by EMO/HLO HydroTel Status and Level Period Actions & AEP Routine Surveillance Day, Night & Alert L1 EMO Modes 2.35 m Monitor status of Piako P-T Alarm message sent to Road and Waitoa recorder sites. EMO 1 & 2 – Pager Notify: Ringing list No. 2 on Page 42 EMgt Officers – Email
Fully Activate HydroTel Te Aroha Depot – Fax L1 EMO 2.75 m Paeroa Office – Fax Notify: Programme Manager WVS Matamata-Piako DC – HLO Paeroa (Kevin Campbell) Fax Works Supervisor Kerepehi (Ian Sara) Hauraki DC – Email & Works Supervisor Te Aroha Fax (Roger Spooner)
If level is expected to exceed 2.80 m, contact… Ringing List No. 3 on page 42 Fully Activate HydroTel L1 EMO 2.95 m If level is expected to exceed 3.0 m; Notify: Ringing List No. 4 on Page 43 Continue to update information and inform the necessary persons (as above) as appropriate. Kerepehi Works Supervisor (Ian Sara) should already have arranged reading gaugeboards (Waikaka to Kaihere Ferry) to be forwarded by cellphone to the EMO 1. Note: Stopbank overflow at Maukoro Landing is 3.35 m. Notify: Civil Defence Controller 3.30 m (Hamilton) (EW)
Monitor All relevant sites and advise Civil Defence of possible flood warning
Page 38 Doc # 761111
Ringing List No. 1: P-T Road Contact Number Area Affected Mr Fraser-Jones 07 887 5780 No.8 Rd Leo Arson 07 843 7263 d/s West Rd Bridge or Linda Arson 07 862 8652 (work) Brosnan 07 887 5511 d/s West Rd Bridge Mr M Peacock 07 887 5621 Confluence Fax: 07 887 5686
Ringing List No. 2: Maukoro Landing Contact Number Area Affected Steve Clark HDC 025 961 726 M Peacock 07 887 5621 Confluence 0274 964851 Fax: 07 887 5686 Aitchison 07 887 8803 Maukoro landing North Fax: 07 887 8749 Pratt (Bros) 07 887 8853 Pte Waikaka South 07 887 8856 Pte
Ringing List No. 3 Contact Number Area Affected Russell Shanks 07 887 5722 Confluence/West Rd Fax: Same as phone # Michael Peacock 07 887 5621 Confluence 0274 964851 Fax 07 887 5686 John Drent 07 887 8838 Maukoro Landing Fax: 07 889 8769 Keith Hunter 07 887 8820 Waikaka Canal North Fax: 07 887 8920 or Peter Hunter 07 887 8806 Gary and Karen Zydenbos 07 887 8817 Tramline Rd South JW Kowalski 07 887 8801 Tramline Rd South or PC Kowalski 07 887 8885 Ian Troughton 07 867 5114 Tramline Rd 0274 958 270 Victor Meiller 07 887 8804 Mangawhere Rd 021 334 730 Frans Spreeuwenburg 07 867 5189 Mangawhero Rd B Brown 07 867 7071 Mangawhero Rd KR Gill 07 867 6838 Fax: 07 867 6838 Roger Brownlee 07 8678108 Rawe Rawe Rd
Flood Warning Procedures Manual 2003 Page 39 Ringing List No. 4 Contact Number Area Affected Owen Passau a/h 07 884 8855 or 025 294 1097 Roger Spooner a/h 07 884 8603 or 025 971 747 Ian Sara 07 867 6836 or to arrange gauge readings 025 972 698 d/stm of Maukoro Landing Ewan Thompson SH27 Peter Patterson 07 887 8897 Fax: 07 887 8898 Henry Geerts 07 887 5892 hm Maukoro Line Stopbank 07 887 5899 Cowshed Fax: 07 887 5898 Robert McDuff 07 867 6600 Murray Fisher 07 867 6797 Horseshoe Bend Area Wayne Bennett 07 867 7572 Fax: 07 867 7292 Mobile: 025 868113 Maurice Eccles 07 867 7175 Fax: Same as phone # 025 2905878 Don Challis 07 867 7097 Bruce Gordon 07 867 7436 [email protected]
Piako River at Paeroa-Tahuna Rd Return Periods Return Period (yrs) 2.33 5 10 20 50 100 Gauge Height (m) 6.43 7.04 7.32 - - - Discharge (m3/s-1) 80 145 200 250 330 380
Note: Return periods for Maukoro Landing are not available due to the tidal influence at the site.
Page 40 Doc # 761111
Waikato River - Procedures
Background Information The Waikato River is New Zealand’s longest river (425 km). It rises from its headwaters on the slopes of Mt Ruapehu and flows in a generally northerly direction via Lake Taupo, to exit into the sea at Port Waikato. The Waikato River has a total catchment area of some 14,250 km2. The single largest tributary of the Waikato River is the Waipa River, originating in the Rangitoto Ranges in the southern King Country.
Interesting facts on rainfall at Hamilton Continuous records began 1998 Highest 24 hour rainfall total 71 mm on 9th April 2000 Maximum recorded annual rainfall total 1066 mm in 1999 Mean annual rainfall total 947 mm Minimum recorded annual rainfall total 884 mm in 2000
Why provide Flood Warnings? Environment Waikato provides flood warnings for this river system because:
1. The Lower Waikato River is a major system flowing through low lying, highly productive land 2. Areas outside the flood scheme area are becoming further developed, and more people require warnings 3. Its “track record” suggests that it is prone to severe floods (although the risk has been significantly reduced since the completion of the protection scheme). 4. Potential impacts include the closure of major transport links (SH1 and main trunk rail line) and the isolation of rural communities. 5. Many river berms are grazed and farmers need timely warnings to move stock. 6. It provides vital information and assurance for the local Civil Defence organisation during major events. 7. It provides vital information for floodway managers to efficiently control floodpump/gate operations during times of high flows.
Telemetered flood warning stations related to this river system are:
Rainfall: Mangaokewa River @ Te Kuiti Mangaokewa @ Wharekiri Puniu Catchment @ Ngaroma Waikato Catchment @ Hamilton (Environment Waikato Roof) Waikato Catchment @ Hamilton AWS (MetConnect) Mangatangi Catchment @ SH2 Matahuru Catchment @ Maungakawa …plus the MRP sites
Water Level: Taupo Lake Level (MRP) Waipa River @ Otewa Waipa River @ Otorohanga Puniu River @ Pokuru Bridge Waipa River @ Whatawhata Karapiro Lake Level (MRP) Waikato River Discharge @ Karapiro (MRP) Waikato River @ Hamilton
Flood Warning Procedures Manual 2003 Page 41 Waikato River @ Ngaruawahia Mangawara River @ Jefferis Waikato River @ Huntly Waikato River @ Rangiriri Matahuru River @ Waiterimu Waikare Lake Level Lake Waikare Gate Te Onetea Gate Waikato River @ Mercer (Control Structure) Whangamarino River @ Control Structure Whangamarino River @ Ropeway Whangamarino River @ Falls Road Mangatangi River @ SH2 Upper Waikato River This section of the river is largely controlled by the presence of eight hydro-electric dams located between Taupo and Karapiro (see also 1.6.2 below) operated by MRP. While the dams can be used to control (i.e. slow down) the flood peaks, Lake Taupo is the only designated flood storage area in the system.
The river channel between Taupo and Karapiro is generally deeply incised. Hence no flood warning system is located within this reach. Any flooding that does occur is usually isolated and of relatively short duration. However, it is worth noting that wave attack (and associated flooding) is likely on the foreshores of the hydro lakes. This effect is exacerbated when levels are high and/or there are strong onshore winds. Emergency Management Officers are likely to receive calls related to this, in which case the caller should be transferred onto MRP (Ph (07) 857 0110). Genesis Ph (07) 386 1210.
Management with Respect to the Waikato Hydro-Electric System The Waikato Flood Management Rules 2001 outlines the flood management procedures adopted by MRP in balancing the flows in the upper/middle Waikato System (a copy is held in the EMO satchel). In the normal course of events, MRP will be conserving flow and building up storage with the constant outflow from Karapiro being based upon electricity demand only. The MRP management strategy is based on five phases. These are discussed in the above report (which should be read in conjunction with Environment Waikato’s own flood rules and this manual).
Note: EMO 1 should be very familiar with these phases
The level of Lake Taupo and flows in the Waikato Hydro System are available at all times on 0800 820 082.
Lower Waikato River This reach of the Waikato River is largely protected by a comprehensive river control scheme designed to provide flood protection and drainage improvements within the floodplains of the Lower Waikato and Waipa Rivers. Between Karapiro and Ngaruawahia (i.e. including Cambridge and Hamilton), the river is deeply incised and no direct flood control schemes are required.
The scheme is designed to handle a maximum flow of about 1800 cumecs. The limiting design flood is the 1% AEP (or 100 year recurrence interval) except for specific areas where a lower standard of protection was adopted for economic reasons.
Further information can be found in the Lower Waikato Waipa Control Scheme – Asset Management Plan Volume 1 June 1997.
Page 42 Doc # 761111
Management of the Lower Waikato System will be based on information from the succession of stations from Hamilton downwards and knowledge of what is being produced by the Waipa River and Karapiro Dam outflow. There will be some form of discussion with the appropriate staff from the relevant District/City Councils and MRP (see below for contact details). It is assumed that District/City Council Staff will undertake the appropriate action on the information given (including field checks of pump/sewerage stations etc).
Community Gate Operations Refer Section 1.6.18 below.
Rangiriri Spillway When River flows at Rangiriri exceed about 1350-1370 cumecs (8.81 m), a section of the stopbank acts as a spillway (as demonstrated in July 1998). Flood water will then flow across SH1 and onto adjacent farmland. It is then channelled along the main trunk railway line embankment and into the Te Onetea Stream to flow into Lake Waikare, which temporarily stores the water until the flood peak passes Mercer. The Lake Waikare Gate will then be opened to allow the floodwater to flow into the Whangamarino wetland via the Whangamarino River, ending up back in the Waikato River.
The township of Rangiriri is protected from the spillway and lake floodwaters by a small stopbank constructed immediately south of the town.
For further information, see the “Flood Hazard Identification Report – Waikato District 1:50,000 February 1998” by Kelly Barnett.
Travel Times Revised flood wave travel times for the July 1998 flood peaks in the lower Waikato (by Hydraulic Modelling Services) are:
Ngaruawahia to Huntly = 2 hours Ngaruawahia to Rangiriri = 6 hours Rangiriri to Control Structure = 14 hours
Flood Warning Procedures Manual 2003 Page 43 Flood Procedures (Waikato River at Hamilton) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP < mean Routine Surveillance Day, Night & Alert Modes annual L1 EMO 14.0 m Carry the L1 Pager and Alarm message sent to Cellphone at all times Monitor Karapiro outflow and EMO 1 & 2 – Pager Hamilton flow data (travel time = 7.8 hrs) EMgt Officers – Email Respond to customer and media enquires. Issue media Hamilton City C – Fax & releases as appropriate Email through the Media Manager Encourage use of 0832 Waikato DC – Pager, Infolines + Environment Fax & Email Waikato’s Website Maintain Flood Log (File 30 08 MRP – Fax & Email 05) If necessary, manage the Waikato River Watch - system with MRP as per the Fax flood rules (Section 1.6.2)
Notify: Bill Featherstone (HCC) Ph 838 6699 Ray Pooley, Emergency Management Officer (HCC) Ph 838 6699 or Mobile 021 961 749. Fax 838 6599 Waipa Delta (Ph 854 7813 or 025 757 638)
Inform them that the Grantham St Carpark and sections of the Community Paths are likely to be inundated. Level at which the water reaches Grantham St carpark is approx. 14.1 m.
< 5 years Fully Activate HydroTel (20% AEP) L1 EMO 15.0 m As above…
Page 44 Doc # 761111
20 year Fully Activate HydroTel Day, Night & Alert Modes (5% AEP) L1 EMO 16.0m Alarm message sent to As above, and…. EMO 1 & 2 – Pager Inform: HCC that high river levels are EM Officers – Email expected through the city, and that places like Anne St and Hamilton City C – Fax & Awatere Ave could be Email inundated. Check latest weather forecast (from Waikato DC – Pager, MetConnect Page 94) and Fax & Email Karapiro outflow. Anne St kerb affected at 16.1 m (as MRP – Fax & Email measured @ Hamilton Traffic bridge) Waikato River Watch - Fax EMT and relevant Councillors Produce a post-event report Inform HCC that river is approaching the 1998 flood level of 16.76 m
> 50 year Fully Activate HydroTel (2% AEP) L1 EMO 17.0 m As above…and
Inform HCC that the 1998 flood level of 16.76 m has been exceeded
> 100 year Fully Activate HydroTel (1% AEP) L1 EMO 17.5 m As above…and
Inform HCC that breaching of the lowest point of the frontal berm at Alandale could occur at RL ~18.0 m (this is yet to be verified).
Civil Defence Regional Controller
Waikato River at Hamilton: Return Periods Return Period (yrs) 2.33 5 10 20 50 100 Gauge Height (m) 14.62 15.24 15.72 16.16 17.24 17.6 Discharge (m3/s-1) 470 530 590 640 887 957
Flood Warning Procedures Manual 2003 Page 45 A review of Hamilton’s 100 year Design Flood Level was completed in early 2003, by Murray Mulholland, the details of this are in document number 818251. Waipa River – Procedures
Background Information The Waipa River is the major tributary of the Waikato River (catchment area = 3059 km2 representing about 30% of the total Waikato catchment), with its headwater located in the Rangitoto Ranges east of Te Kuiti. It flows in a generally northerly direction through the rolling hills of the King Country, passing through the town of Otorohanga, and finally entering the Waikato River at Ngaruawahia. Major tributaries include the Mangapu, Waitomo, Mangawhero, and the Mangaokewa Rivers.
During pre-scheme days, the Waipa River inflicted great damage to many rural towns and adjacent areas during major floods. Since then (under the LWWCS), major protection works have been constructed to provide a 100 year protection to the towns of Otorohanga and Te Kuiti (on the Mangaokewa River). Between Otorohanga and Whatawhata, the river channel is deeply incised and flooding is therefore considered a low risk within this reach.
Interesting facts on rainfall at Otewa Continuous records began 1981 Highest 24 hour rainfall total 113 mm on 10th and 11th March 1990 as well as 11th and 12th February 2001 Maximum recorded annual rainfall total 1888 mm in 1996 Mean annual rainfall total 1537 mm Minimum recorded annual rainfall total 1258 mm in 1997
Interesting facts on rainfall at Mangaokewa Continuous records began 1989 Highest 24 hour rainfall total 121 mm on 8th and 9th July 1998 Maximum recorded annual rainfall total 2014 mm in 1996 Mean annual rainfall total 1766 mm Minimum recorded annual rainfall total 1266 mm in 1999
Why provide Flood Warnings? Environment Waikato provides flood warnings for this river system because:
1. The Waipa River is a major system flowing through low lying, highly productive land 2. Areas outside the flood scheme area are becoming further developed, hence more people require warnings 3. Its “track record” suggests that it is prone to severe floods (although the risk has been significantly reduced since the completion of the protection scheme). 4. Potential impacts include the closure of major transport links (SH3 and main trunk rail line) and the isolation of many rural communities. 5. Many river berms are grazed and farmers need timely warnings to move stock. 6. It provides vital information and assurance for the local Civil Defence organisations during major events. 7. It provides vital information for floodway managers to efficiently control floodpump/gate operations during times of high flows.
Page 46 Doc # 761111
Telemetered flood warning stations related to this river system are:
Rainfall: Waipa Catchment @ Wharekiri Waipa Catchment @ Te Kuiti Waipa Catchment @ Ngaroma Waipa Catchment @ Otewa
API: Catchment Groupings of API Values (mm) Low Moderate High Extreme Waipa 0-100 100-200 200-300 300+
Water Level: Mangaokewa @ Te Kuiti Waipa River @ Otewa Waipa River @ Otorohanga Puniu River @ Pokuru Bridge Waipa River @ Whatawhata
Flood Procedures (Mangaokewa River at Te Kuiti) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP < mean Fully Activate HydroTel Day, Night & Alert Modes annual L1 EMO 50.0 m Carry the L1 Pager and Alarm message sent to Cellphone at all times Monitor water level at Te Kuiti EMO 1 & 2 – Pager and rainfall at Wharekiri / Te Kuiti EMgt Officers – Email Respond to customer and media enquires Waitomo DC – Fax & Email Encourage use of Environment [email protected] Waikato WebSite & Fax 07 878 7771 0832 Infolines Maintain Flood Log Tranz Rail – Fax (File 30 08 05) MAF – Fax & Email Inform: Waitomo District Council of 07/07/02 14:45 1m to New possible inundation of northern World Supermarket, Peter suburb. Ph 07 878 8801 or 029 McGregor 021 867 485 878 6006 (John Moran)
= mean Fully Activate HydroTel annual L1 EMO 51.0 m As above
= 10 year Fully Activate HydroTel (10% AEP) L1 EMO 52.0 m As above…and
Advise that river is approaching the 1998 flood peak of 52.7 m.
Flood Warning Procedures Manual 2003 Page 47 Mangaokewa River at Te Kuiti: Return Periods Return Period (yrs) 2.33 5 10 20 50 100 Gauge Height (m) 51.2 51.65 52.0 52.35 52.72 53.05 Discharge (m3/s-1) 60 80 96 112 132 148 Flood Procedures (Waipa River at Otewa) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP L1 EMO Day, Night & Alert Modes Routine Monitoring Alarm message sent to 4.0 m EMO 1 & 2 – Pager EMgt Officers – Email L1 EMO Otorohanga DC – Text & Approaching 1998 flood Email messages 4.8 m level of 5.15 m NIWA-Hamilton – Email Ring David Hall at ODC on MAF – Fax & Email 07 871 9334 or 021 650 414 Otewa Landowner Engineer Ian Gooden 0211 (J Bojosen-Tapca) - Fax 562 858 Flood Procedures (Waipa River at SH31 Bridge Otorohanga) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP L1 EMO Day, Night & Alert Modes Routine monitoring Alarm message sent to 31.5 m EMO 1 & 2 – Pager EMgt Officers – Email L1 EMO Otorohanga DC – Text & Approaching1998 flood level Email messages 32.8 m of 33.38 m Tranz Rail – Fax
Ring David Hall at ODC on MAF – Fax & Email 07 871 9334 or 021 650 414 Engineer Ian Gooden 0211 562 858 Flood Procedures (Puniu River at Barton’s Corner Rd Bridge) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP L1 EMO Day, Night & Alert Modes Routine monitoring 12.5 m Alarm message sent to
Fully Activate HydroTel EMO 1 & 2 – Pager L1 EMO 13.5 m EMgt Officers – Email Advise that river is approaching the 1998 flood Waipa DC – Fax & Email peak of 13.98m. MAF – Fax & Email
Page 48 Doc # 761111
Fully Activate HydroTel L1 EMO 14.5 m
Advise that river has exceeded the 1998 flood peak of 13.98m.
Flood Procedures (Waipa River at SH23 Bridge Whatawhata) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP < mean Fully Activate HydroTel Day, Night & Alert Modes annual L1 EMO 15.5 m Monitor Karapiro outflow Alarm message sent to and Ngaruawhia flow data (travel time = 12.7 hrs) EMO 1 & 2 – Pager Monitor Otorohanga Water Level Recorder (travel time EMgt Officers – Email = 11 hours) and Rainfall intensity at Ngaroma, Te Waipa DC- Fax & Email Kuiti and Otewa Monitor Puniu Water Level Waikato DC – Pager, Fax Respond to customer and & Email media enquires Encourage use of 0832 MAF – Fax & Email Infolines + Environment Waikato Website for River Landowner (K Holmes) – Levels & Rainfall Fax Maintain Flood Log (File 30 08 05) MRP – Fax & Email Inform: Waikato District Council of NIWA-Hamilton - Email possible inundation of Bedford Rd. Ph 07 824 8633 Waipa District Council Engineer Eddie Shadrock Ph 07 871 7133 (office hours only) or 0292 753 365 = mean Fully Activate HydroTel annual L1 EMO 16.5 m As above, and… Inform: Duty Utilities Officer at Waikato District Council of possible Te Kowhai Flood. Ph 07 824 8633 Fully Activate HydroTel L1 EMO 18.0 m As above,
= 20 year Fully Activate HydroTel (5%AEP) L1 EMO 19.0 m As above, and advise the river approaching 1998 Flood Level 19.56m
Flood Warning Procedures Manual 2003 Page 49 Waipa River at Whatawhata: Return Periods Return Period (yrs) 2.33 5 10 20 50 100 Gauge Height (m) 16.1 17.6 18.4 19.1 20.0 20.6 Discharge (m3/s-1) 431 577 672 763 878 963
Note: 1998 flood level = 19.56m.
Page 50 Doc # 761111
Waikato River below Waipa River – Procedures The lower reaches of the Waikato River are tidal, to calculate the high and low tides visit, http://www.niwa.co.nz/services/tides.
API: Catchment Groupings of API Values (mm) Low Moderate High Extreme Lower Waikato 0-100 100-200 200-300 300+
Flood Procedures (Waikato River at Ngaruawahia) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP 10.5 - None. This is a temporary alarm set Alarm message sent via up for the Horotiu Landfill. fax and email to Perry Waste Services & Contacts: HCC Refuse Staff Manager of Perry Waste Services Peter Higgs (Ph 838 6998, Fax 8299819) or Bill Mitchelmore (Cell 025 953 071) HCC Refuse Engineer Alex Tautau (Ph 838 6787, Cell 021 902 572, Fax 838 6998) or Howard Mitchell (Ph 838 6992). Fully Activate HydroTel Day, Night & Alert Modes L1 EMO 11.9 m Monitor Karapiro, Hamilton Alarm message sent to and Whatawhata flows Respond to customer and EMO 1 & 2 – Pager media enquires Notify all relevant TLA’s EMgt Officers – Email Encourage use of 0832 Infolines and Environment Waikato DC – Pager, Waikato Website River Fax & Email Levels & Rainfall Maintain Flood Log (File 30 MAF – Fax & Email 08 05) MRP – Fax & Email Inform: North Waikato Works Tranz Rail - Fax Supervisor (025 738068) EMT and relevant Councillors
Advise that this will be about 1.2m to 0.9m below design flood level @ Rangiriri
Flood Warning Procedures Manual 2003 Page 51 Fully Activate HydroTel L1 EMO 12.6 m As above, and…
Inform: EMO1 to contact WDC Duty Controller by phone to confirm notification of alarm (Pager 026 2579940)
Fully Activate HydroTel L1 EMO 13.25 m As above, and…
Inform: Work supervisors to patrol stopbanks Report conditions to EMO 1 on regular basis Inform Huntly Police of situation with special attention to Hakanoa and Huntly West Fully Activate HydroTel Day, Night & Alert Modes L1 EMO 13.75 m As above Alarm message sent to
This will be about 0.4m and 0.2 EMO 1 & 2 – Pager m below design flood level at Rangiriri. Approaching 1998 EMgt Officers – Email flood level of 14.2m Fully Activate HydroTel Waikato DC – Pager, L1 EMO Fax & Email 14.25 m As above This will exceed about 0.2 m MAF – Fax & Email below design flood level at Rangiriri. Tranz Rail – Fax Inspections of stopbanks (at Rangriri spillway and Huntly) are to be continuous Huntly residents on all land below DFL to be alerted by Civil Defence that evacuation is possible
Waikato River at Ngaruawahia: Return Periods
Return Period (yrs) 2.33 5 10 20 50 100 Gauge Height (m) 11.38 12.08 12.55 12.99 13.57 14.01 Discharge (m3/s-1) 724 914 1057 1207 1423 1604
Page 52 Doc # 761111
Flood Procedures (Waikato River at Huntly Power Station) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP Fully Activate HydroTel Day, Night & Alert Modes L1 EMO 9.8m Monitor Ngaruawhia flow Alarm message sent to data (travel time =5 hrs) Respond to customer and EMO 1 & 2 – Pager media enquires Consult the Huntly Flood EMgt Officers – Email Mgt Plan Encourage use of 0832 Waikato DC – Pager, Infolines and Environment Fax & Email Waikato website Maintain Flood Log (File 30 MAF – Fax & Email 08 05) Produce a post-event report Tranz Rail – Fax Inform: Huntly College Principal Ph NIWA-Hamilton - Email 07 828 7152 or A/H ?? Lower Waikato Works Supervisor A/H 07 855 7620 EMT and relevant Councillors Fully Activate HydroTel Day, Night & Alert Modes L1 EMO 10.5 m As above, and… Alarm message sent to
Inform: EMO 1 & 2 – Pager HydroTel also faxes WDC Ngaruawahia office EMgt Officers – Email EMO1 to contact WDC Duty Controller by phone to Waikato DC – Pager, confirm. Fax & Email Fully Activate HydroTel L1 EMO MAF – Fax & Email 11.0 m As above, and… Tranz Rail – Fax Inform: HydroTel pages Waikato NIWA- Hamilton – Email District Duty Controller automatically. (026 10/7/02 9:45am ponding 2579940) at Parry St. HydroTel also faxes WDC Ngaruawahia office EMO1 to contact WDC Duty Controller by phone to confirm. Approaching 1998 flood level of 11.24m
Flood Warning Procedures Manual 2003 Page 53 Waikato River at Huntly – Tainui Bridge: Return Periods Return Period (yrs) 2.33 5 10 20 50 100 Gauge Height (m) 9.43 9.96 10.26 10.53 10.84 11.06 (11.25) (11.57) (11.86) Discharge (m3/s-1) 809 1009 1136 1254 1402 1510
Note: the 100 year scheme design flow at Huntly is 1840 cumecs.
Page 54 Doc # 761111
Flood Procedures (Waikato River at Rangiriri) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP < mean Fully Activate HydroTel Day, Night & Alert Modes annual L1 EMO 7.0 m Alarm message sent to Check community gate settings on page 69 EMO 1 & 2 – Pager (especially Te Onetea - which should now be closed). EMgt Officers – Email
Waikato DC – Pager, Fax & Email
MAF – Fax & Email
Tranz Rail – Email 5 years Fully Activate HydroTel Day, Night & Alert Modes (20% AEP) L1 EMO 8.0 m Monitor Ngaruawhia and Alarm message sent to Rangiriri flow data (travel time =13 hrs) EMO 1 & 2 – Pager Respond to customer and media enquires EMgt Officers – Email Encourage use of 0832 Infolines + Environment Waikato DC – Pager, Fax Waikato Website River & Email levels & Rainfall Maintain Flood Log (File MAF – Fax & Email 30 08 05) If necessary, manage the Tranz Rail – Email system with MRP as per the flood rules (Section If overflow is likely: 1.6.2) Instruct Transit New Produce a post-event Zealand to remove the report safety barrier (wire rope) on the median of SH1 Inform: adjacent to the spillway. OPUS International (Ph This is to prevent debris 025 785 989 or Tony being trapped. Burnetti 027 436 2608) and Tranz Rail (Ph 07 846 Contact: Brad Hayes 8463 or 025 978 329) of [email protected] possible spillway overflow, (occurs at 8.80 m) Assets Engineer to monitor Community Gate Settings (section 1.6.18) EMT and relevant Councillors 100 year Fully Activate HydroTel (1% AEP) L1 EMO Hamilton 8.5 m As above,
Flood Warning Procedures Manual 2003 Page 55 > 100 Fully Activate HydroTel year L1 EMO Hamilton 9.0 m (1% AEP) As above, and… Approaching 1998 flood level of 9.06m.
Waikato River at Rangiriri: Return Periods Return Period (yrs) 2.33 5 10 20 50 100 Gauge Height (m) 7.81 7.96 8.11 8.25 8.42 8.53 Discharge (m3/s-1) 940 1000 1060 1120 1190 1240
Flood Procedures (Waikato River at Whangamarino Control Structure) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP < mean Routine Monitoring Day, Night & Alert Modes annual L1 EMO 3.25m Alarm message sent to Morrison Rd Drain Floodgate should close automatically at EMO 1 & 2 – Pager ~3.4 m to prevent backflow. EMgt Officers – Email Note: Water will accumulate on the landward side of the Waikato DC – Pager, Fax floodgate due to internal & Email ponding.
Page 56 Doc # 761111
= mean Fully Activate HydroTel Franklin DC – Faxes annual L1 EMO (Ronnie Gram & Mark 4.5 m Monitor Rangiriri flow data Ball) (travel time = 17 hrs) Respond to customer and MAF – Email & Fax media enquires. Issue media release through the Tranz Rail – Email media manager Encourage use of 0832 Waikato River Watch – Infolines + Environment Fax & Email Waikato Website River Levels & Rainfall Mercer Landowners Maintain Flood Log (File (Jeanette Thomas, Ken 30 08 05) Holmes, Martin Hansen & If necessary, manage the Mark Bon) system with MRP as per the flood rules (Section 1.6.2) 10/07/02 event - water Produce a post-event trickled over a 1m section report on Thomas property
Inform: Ringing List No. 1 on Page 57 Advise that Morrison Road Compartment begins to flood (internal pond level during July 2002 event reached 4.05 m) Southern Compartments begin to flood (~50mm depth) at 4.83 m for Sampsons and 4.93 m for Logans EMT and relevant Councillors
Flood Warning Procedures Manual 2003 Page 57 10 year Fully Activate HydroTel (10% AEP) L1 EMO 5.0 m As above, and advise that…..
Berm overflow is in process at properties adjacent to the Whangamarino River 5.07 m = overtopping level d/s of rowing club 5.10 m = overtopping level 100 m u/s of rowing club 5.4m, SH1 overflow likely, notify Transit Staff board reading at Mercer 10.20am on 13/7/02 Farrell property SH1 water lapping at 5.43m 5.46m 100mm below SH1, opposite Crocus Farms, Lapping Crocus Farms stopbanks, crossing SH1 at Farrell’s 100 year Fully Activate HydroTel (1% AEP) L1 EMO 5.5 m As above
100 year Fully Activate HydroTel (1% AEP) L1 EMO 6.0 m As above, and advise that…..
River approaching 1998 flood level of 6.11m
Travel Times (hr.mins) NOT decimal
Location Flow (m3/s) 150 330 530 1660 Ngaruawahia 10.00 7.18 6.06 4.12 Huntly 15.42 11.30 9.48 7.12 Rangiriri 21.18 15.24 13.24 9.48 Mercer 25.24 21.06 18.54 18.36 Tuakau 32.00 24.00 24.12 21.30
Page 58 Doc # 761111
Flood Procedures (Waikato River at Mercer) New recorder, alarm levels yet to be set.
Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP
m
m
m
m
Flood Warning Procedures Manual 2003 Page 59 Ringing List No.1 Contact Number Area Affected/Designation Shirley/Richard Logan 09 233 4444 Morrison Rd resident Dave Sampson 09 233 4420 Morrison Rd resident [email protected] Cr Jeanette Thomas 09 232 6771 (fax) Morrison Rd resident (Councillor) Ashley Thomas 0274 906 770 Cr Thomas’ Son. 09 233 6565 (ph/fax) Morrison Rd Paul/Kathleen Symes 07 826 3811 or next to Whangamarino 0274 857 398 Control Structure Ken Holmes 07 855 6747(fax) ex-Councillor (Hamilton) 025 764 082 Maree Bernasconi Fax: 09 2387917 Rowing Club [email protected] Clive Woodward 09 233 4436 Smeed Rd resident Fax: Same as phone # [email protected] Mike Peters 07 – 8264281 Mere Mere East Drainage 0274758984 District and Mere Mere West 07 – 8264381 (FAX) Drainage District Malcolm Lumsden 07 828 8100(fax) Lower Waikato Riverwatch [email protected] (Chair) Crocus Farms Glennis Aro 09 274 6145 Farmers adjacent to 09 233 6308 Mangatawhiri River Malcolm Lea (Farm Manager) Sue Lamont 09 232 6833 Waikato River, opposite Fax: Same as Phone # Mangatawhiri confluence Garry McGuire 09 236 8144(fax) Lower Waikato Riverwatch (Sec). Tuakau Drainage Area Chairman. Ronnie Gram 09 237 1300 (wk) Franklin District Council (025) 289 0203 09 238 3882 (a/h) (Engineer) Mark Ball 09 238 6995 (wk + fax) Franklin District Council 0274 514 942 (cell) (CDO) 09 238 2995 (home) 026 242 1521 (pager) Fed-Farmers (07)838 2589 (wk) (Grant Kessell) Community Asset Duty Officer 0274 527 536 Waikato District Council Roading Officer Pager 026 2000 975 MRP 07 857 0110 Control Centre Operator Tranz Rail (Wayne Stewart) 07 846 8463 (wk) Track Structures Manager 07 843 3273 (hm) 0274 978 329 (cell)
Page 60 Doc # 761111
Roading Consultants Contact Number Franklin DC Contractors: Tom Kettle (09) 237 1473 OPUS Consultants, Pukekohe (0274) 873 685 Transit Area Network (07) 838 2980 Maintenance Contractors: (07) 838 2591 (fax) Duffal, Watts & King Clement Fernando (07) 838 8107 Works Infrastructure 0800 009 920 (24 hr#) Transit Rangiriri Project Ron Boyle (07) 838 0144 Manager: (025) 748 318 Bloxham, Burnett & Oliver John Kerr (025) 860 585
Waikato River at Whangamarino Control Structure: Return Periods
Return Period (yrs) 2.33 5 10 20 50 100 Gauge Height (m) 4.51 4.86 4.99 5.12 5.30 5.39 Discharge (m3/s-1) 950 1070 1120 1170 1240 1280
Flood Procedures (Whangamarino River at Ropeway) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP Fully Activate HydroTel Day, Night & Alert Modes L1 EMO 5.0 m Alarm message sent to Fully Activate HydroTel L1 EMO EMO 1 & 2 – Pager 5.5 m Approaching 1998 flood level of EMgt Officer - Email 5.63m.
Fully Activate HydroTel L1 EMO 6.0 m Level has exceeded 1998 Flood Level
Flood Warning Procedures Manual 2003 Page 61 Flood Procedures (Community Gate Operation & Setting) Three community gates, which form part of the Lower Waikato/Waipa Control Scheme were constructed in the 1960’s by the Waikato Valley Authority in consultation with the local community (see Map 7.1 below).
The small Te Onetea Community Gate is operated to meet fishery requirements and is normally open. Before the gate was constructed, water used to flow naturally between Lake Waikare and the Waikato River via the Te Onetea Stream. Telemetry levels for Rangiriri +0.14 m can be compared to Lake Waikare levels to indicate in which direction the flow will be. The gate may be opened up to 1 metre unless Lake Waikare is rising more than 0.05 m/day or Rangiriri level is greater than 7.00 m, when it should be closed. It should also be closed when Lake Waikare’s level is higher than the Waikato River level.
The gate operates automatically (i.e. computer controlled).
The water then flows into Lake Waikare, where the Community Gate at the northern end of the lake regulates the level for either flood storage or for routine levels required by a lake-level fixing policy worked out with the community. The water flows into the Whangamarino River via an outlet canal which is stopbanked. Design level of the lake is 7.8 m. The 1998 flood level was 6.29m.
Note: The Lake Waikare Gate is an automatically operated system. To adjust the setting, or to find out the current setting, open the Lake Waikare station detail screen page in HydroTelTM.
The Whangamarino Control Structure (WCS) Community Gate will always either be completely opened or completely closed, governed by the direction of water flow. The gate is left open most of the year, although in large floods the gate is closed to prevent the Waikato River from backflowing into the swamp. Design level is 5.85 m (max recorded is 6.11 m – before the gate was installed). When this gate is closed, the Lake Waikare gate should also be closed.
All queries regarding the gate settings of the Te Onetea, Lake Waikare, and the Whangamarino Control Structure community flood gates should be directed to:
Ghassan Basheer (Assets Engineer), Environment Waikato
Work Ph: (07) 856 7184 Ext 8761 A/h (07) 855 1620 if he is unavailable, contact;
Murray Mulholland (Technical Services Manager), Environment Waikato
Work (07) 856 7184 Ext 8883 A/h (07) 858 4994
Waikato Community Gate Operational Procedures follow on the next page.
Page 62 Doc # 761111
Lake Waikare Typical Values and Control Setting
Min Max Mean 5.34 m 6.05 m 5.59 m
Routine Operation Table: Lake Waikare
PERIOD April 1-Sept 30 Oct 1-Dec 31 Jan 1-Mar 31
CONTROL LEVEL 5.50 m 5.65 m 5.60 m
Present Level Gate Settings
< 5.50 0-50 mm 0-0 0-0
5.50-5.60 50-200 mm 0-0 0-50 mm
5.60-5.70 200-610 mm 0-200 mm 0-200 mm
5.70-5.80 610-1220 mm 200-610 mm 200-610 mm
5.80-5.90 1220-1220 mm 610-1220 mm 610-1220 mm
> 5.90 1220-1220 mm 1220-1220 mm 1220-1220 mm Use lower setting for low end of range and no predicted rain. Use high setting for high end of range and rain expected.
Courtesy Call (if gates are being opened or closed so he can move nets)
Gary Watson (Eel Fisherman) Ph 07 826 3830 or 025 274 7308
Jack Kelly Ph (07) 826 7786
Flood Warning Procedures Manual 2003 Page 63 Map 7.1
Community Gate Operations (Note: Diagram not to scale) Maramarua River KEY Community Mercer Gate N Settlement Meremere
Whangamarino Waikato River Swamp (Main Channel)
SH 1 Whan gamarino River Main Trunk Outlet Canal Rangiriri Te Onetea Rangiriri Stream Spillway Lake Waikare
Ohinewai Matahuru Stream
Flood Procedures (Matahuru Stream at Waterimu Rd) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP Fully Activate HydroTel Day, Night & Alert Modes L1 EMO 7.5 m Alarm message sent to Fully Activate HydroTel L1 EMO EMO 1 & 2 – Pager 8.0 m
Fully Activate HydroTel L1 EMO 8.5 m Approaching 1998 flood level of 8.60m.
Page 64 Doc # 761111
Mangawara River - Procedures
Background Information The Mangawara River is a major tributary of the Lower Waikato River, with the confluence being located at Taupiri. The headwaters are situated in the steep Hapuakohe Ranges east of Lake Waikare. The river flows generally in southwest direction, passing north of the township of Hoe-o-Tainui. The Mangawara has two main tributaries, the Komakorau and the Tauhei Streams. The total catchment area of the Mangawara system is 620 km2.
The Mangawara River flood protection works form part of the Section D works of the Lower Waikato Waipa Control Scheme. The main components of the scheme include stopbanks equipped with floodgates, detention dams and the construction of two spillways north of Hoe-O-Tainui. These are the Smith’s and Southee’s Spillways.
Southees Spillway (NZMS 260 S13 247 071) This was designed in 1975 under the direction of the Waikato Valley Authority, and is 40.8 m above MSL (Moturiki). The spillway is located 200m downstream of the Hoe-O- Tainui Bridge. It operates when river flow exceeds 42.50 cumecs (mean annual return period design). The floodwater is diverted into the Paranui Canal via overland flow across Tainui Road and adjacent farmland. The road is subject to closure in extreme events.
Smiths Spillway (NZMS 260 S13 246 069) This was also designed in 1975 by the Waikato Valley Authority, and is 38.3 m above MSL (Moturiki). The spillway is located a further 300m downstream from the Southees Spillway. It operates when river flow exceeds 28.32 cumecs (mean annual return period standard). The floodwater is also diverted into the Paranui Canal via artificially contoured sections of farmland. Tainui Road is unaffected by the operation of this spillway.
Due to it being at a lower level, the Smith’s Spillway (on average) operates more frequently than it’s upstream brother. As an indication only (due to the distance downstream from the spillways), the flood team in Hamilton can assume that the Smiths Spillway has operated when the Jefferis water level recorder reaches or exceeds 20.0 m.
Paranui Canal The Paranui Canal is designed to divert water from the spillways into the Mangawara River further downstream at Jefferis Bridge. The Paranui Canal is stopbanked on both sides and flooding out of the drain is considered a low hazard due to the 50 year return period design. Statistics of the Mangawara Scheme Design Standard: 50 year frequency Design Discharge: 337 Cumecs (at outlet) Benefitting Areas: Direct 6620 ha Indirect 4000 ha = 10,620 ha
Further information can be found in the “Lower Waikato Waipa Control Scheme Asset Management Plan 1997”, “Flood Hazard Identification Report Waikato District 1:50,000 1998.
Flood Warning Procedures Manual 2003 Page 65 Why provide Flood Warnings? Environment Waikato provides flood warnings for this river system because:
1. The Mangawara River is a major system flowing through low lying, highly productive land 2. Areas inside and outside the flood scheme area are becoming further developed, hence more people require warnings 3. Its “track record” suggests that it is prone to severe floods (although the risk has been significantly reduced since the completion of the protection scheme). 4. Potential impacts include the closure of major transport links (Tainui Rd, Tauhei Rd) and the isolation of many rural communities. 5. Many river berms are grazed and farmers need timely warnings to move stock (e.g. Jefferis Bridge to Olds Road on the Mangawara River, Sludge Creek area, Tauhei return banks - Mangawara to Orini/Taupiri Rd, Murchies Drain area). 6. It provides vital information and assurance for the local Civil Defence organisations during major events. 7. It provides vital information for floodway managers to efficiently control floodpump / gate operations during times of high flows.
Telemetered flood warning stations related to this river system are:
Rainfall: Kaihere / Matahuru Catchment @ Maungakawa
Water Level: Mangawara River @ Jefferis
The Mangawara River Catchment consists of only one telemetered river level site (Jefferis) and one rainfall site (Maungakawa Flood Procedures (Mangawara River at Jefferis) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP L1 EMO Day, Night & Alert Modes 18.5 m Advise Phillip Ecclestone (North Alarm message sent to Waikato Works Supervisor) of river level and rainfall situation EMO 1 & 2 – Pager at Maungakawa. Ph (025) 738 068. If he is unavailable Phone Emergency Mgt Off - Roger Gee (025 283 6849 or Email (07) 889 3446.
L1 EMO 19.0 m As above.
Page 66 Doc # 761111
Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP Fully Activate HydroTel Day, Night & Alert Modes L1 EMO 19.5 m Alarm message sent to Advise Phillip Ecclestone (North Waikato Works Supervisor) of EMO 1 & 2 – Pager river level and rainfall situation at Maungakawa. Ph (025) 738 Emergency Mgt Off - 068. If he is unavailable Phone Email Roger Gee (025 283 6849 or (07) 889 3446.
Fully Activate HydroTel L1 EMO 20.0 m As above.
Note that Southees spillway operates at about 20.0m.
Fully Activate HydroTel L1 EMO 20.5 m As above.
Approaching 1998 flood level of 20.7m.
Mangawara River at Jefferis: Return Periods
Return Period (yrs) 2.33 5 10 20 50 100 Gauge Height (m) 20.10 20.65 21.05 21.45 21.90 22.25 Discharge (m3/s-1) 54 75 91 107 128 143
Flood Warning Procedures Manual 2003 Page 67 Mangatangi River - Procedures
Background Information The headwaters of the Mangatangi River are located in the Hunua Ranges (i.e. in the Auckland Region). It is a controlled river system under WaterCare Services in Auckland, who operate the Mangatangi Dam and associated reservoir to supply domestic water to Auckland. The reach below the dam is under Environment Waikato’s jurisdiction.
There are flood storage zones at the lower end of the River. The Bell Road stopbank is located alongside the Mangatangi River and in 1998 was subjected to less flooding pressure than those stopbanks in closer proximity to the Waikato River. The stopbank, floodgates and pump station appeared to be in good working condition. However, the protected area was flooded due to the overtopping of the Mangatangi stream near SH2, which led to ponding of approximately 150 hectares on the land side of the stopbank.
During the July 1998 flood event, the Mangatangi stream breached its banks and caused flooding of the Bell Road protected compartment. This was associated with significant erosion of the stream banks. Subsequently, Environment Waikato advised the landowners to form a care group to look at some blockage removal works, planting and fencing off the river banks. The group was established and works undertaken.
Recently, the area suffered two floods within one week, causing flooding of the Bell Road compartment and further significant erosion and washing away, all of the newly planted trees. Landowners asked for advice from Environment Waikato.
Staff have undertaken a site inspection and advised the landowners to formally request a study of the issues, as these are catchment issues, as well as local, and this might include substantial works which are beyond the ability of the land care group to solve on their own.
Why provide Flood Warnings?
Environment Waikato provides flood warnings for this river system because:
1. The Mangatangi River is extremely flashy in nature 2. Areas adjacent to the river are becoming further developed, hence more people require warnings 3. Its “track record” suggests that it is prone to severe floods. 4. Potential impacts include the closure of major transport links (in particular SH2). 5. Many of the lower river berms are grazed and farmers need timely warnings to move stock. 6. It provides vital information and assurance for the local Civil Defence organisations during major events. 7. It provides vital information for floodway managers to efficiently control floodpump/gate operations during times of high flows.
Page 68 Doc # 761111
The Issues
The Mangatangi and Maramarua streams, which join together above SH 2, have a catchment of approximately 170 square kilometres, between the north and eastern ranges and the Bell Road Stopbank. The stream extends further 11 kilometres into the Whangamarino wetland before it joins the Whangamarino River. The Mangatangi stream is controlled at its northern end by a dam, forming a lake, and providing Auckland Region with water supply. The dam is managed by Water Care.
The main issues in this catchment include the following: a. Dam Management
The dam is managed by Water Care for the purpose of water supply to the Auckland Region. Currently, the reservoir is operated so that it holds water close to the spillway level. The normal flow in the Mangatangi stream is very small, mainly generated from the catchment downstream of the dam. During heavy storm events, the reservoir fills very quickly and it spills over creating a wave of high discharge and high velocity flow. This combined with the flows of the same catchment, produces significant flows within a short period of time. The current arrangements with Water Care are very loose, and they don’t provide information in terms of flow over the spillway, spilling warning and other hazard management requirements. Recently the Hazard Team staff have started negotiating new rules and requesting more co-operation.
The Resource Consents for the Mangatangi dam is under review and issues such as effects of the dam on the Mangatangi stream need to be revisited and mitigation sought from the dam operators. b. Erosion Control
The Mangatangi stream suffers from erosion in many reaches due a number of factors. These include, steep gradients, bank material and formation, channel capacity, channel batter slopes, channel geometry and winding, vegetation cover, water level variations and land use.
The area downstream of SH2 suffered major stream bank erosion during this year after two floods within one week. Similar erosion occurred upstream of SH2, and staff received a couple of complaints in that area. This has occurred in 1998 and will continue to happen if protection measures are not looked at seriously, on a catchment scale. c. Flood Control
The area between SH2 and the Bell Road stopbank, suffers from flooding at least annually. This area was not protected under the Lower Waikato Scheme, though it was identified as a flood prone area. While flooding did not seem to be a major issue for the landowners in the past, as it wasn’t so frequent, now it seems to occur more frequently and is affecting the farming activities and economics. Landowners downstream of SH2 are seeking solutions for the flooding problems. d. General River Management
It is obvious that a consistent river management approach is required for this catchment. This might include consultation with landowners, education programmes and a land care approach to undertaking works. It also includes co-ordination of activities, and consultation with major stakeholders such as Franklin District Council, Waikato District Council, Water Care and the Department of Conservation.
Flood Warning Procedures Manual 2003 Page 69 Auckland Regional Council is required to pass on certain information concerning the level of the Mangatangi and Mangatawhiri Reservoirs if flood conditions are developing (i.e. Mangatangi above 196.20 m and rising, Upper Mangatawhiri less than 0.50 m below spillway level and rising). This information will normally only be used for assessing the situation but standing instructions to ARC give some relief below the Mangatangi Dam as follows: a) Level above 194.75 m Moturiki - maximum normal draw-off b) Level above 196.27 m Moturiki - spillway flow
Flood Alarm Procedures
Watercare Services’ telemetry system will automatically notify the EMO 1 (by text message) when:
1. Dam level rises above 150mm below overflow:
Expected Message: "Mangatangi Dam Level 150mm below overflow and rising"
2. Dam level falls below 300mm below overflow:
Expected Message: "Mangatangi Dam Level 300mm below overflow and falling"
A check on the situation with Franklin DC is also advisable (contact details follow below).
Website Information
Lake level and percentage full data is now available on Watercare’s website (www.watercare.co.nz). This data is collected to manage the resource most effectively, and to indicate when the lakes might overflow, allowing more water into the downstream watercourses.
24 hrs Control Centre
7.30am – 4.00 pm: Ardmore Treatment Plant Ph (09) 292 8634 Peter Dopheide ([email protected])
Afterhours: Church Street Control Centre Ph (09) 634 7840 (Hunua Duty Officer)
Emergency Contacts
Gavin Palmer, Operations Manager, Water, ph 0274 845 556, [email protected].
Brian Park, Hunua Superintendent, ph 0274 938 212, [email protected].
Shayne Cunis, Process Engieer Waikato, ph 027 277 8618, [email protected].
Telemetered flood warning stations related to this river system are:
Rainfall: Mangatangi Catchment @ Mangatangi
Water Level: Mangatangi River @ SH2
Page 70 Doc # 761111
Mangatangi Spillway Rating (Weir Control) 1 H(m) H/Rs C0 (feet units) C0 = Q(cumecs) Co√0.3048 0.50 0.062 4.02 2.22 38.0 0.75 0.094 4.00 2.21 69.4 1.00 0.125 3.98 2.20 106 1.25 0.156 3.94 2.18 147 1.50 0.187 3.91 2.16 192 1.75 0.219 3.87 2.14 239 2.00 0.250 3.82 2.11 289 2.25 0.281 3.77 2.08 340 2.50 0.312 3.73 2.06 394 2.75 0.344 3.67 2.03 447 3.00 0.375 3.60 1.99 500 3.25 0.406 3.55 1.96 555 3.50 0.437 3.49 1.93 610 3.75 0.469 3.42 1.89 650 choking (Table from Doc#843972)
Mangatangi Rating Curve (0.01 – 0.30m) H C (feet units) Q (cumecs) 0.0 4.07 0.00 0.01 4.07 0.11 0.02 4.07 0.31 0.03 4.07 0.56 0.04 4.07 0.87 0.05 4.07 1.21 0.06 4.06 1.59 0.07 4.06 2.01 0.08 4.06 2.45 0.09 4.06 2.93 0.1 4.06 3.43 0.11 4.06 3.95 0.12 4.06 4.50 0.13 4.06 5.08 0.14 4.06 5.67 0.15 4.06 6.29 0.16 4.05 6.93 0.17 4.05 7.59 0.18 4.05 8.26 0.19 4.05 8.96 0.2 4.05 9.67 0.21 4.05 10.40 0.22 4.05 11.15 0.23 4.05 11.92 0.24 4.05 12.70 0.25 4.04 13.50 0.26 4.04 14.32 0.27 4.04 15.15 0.28 4.04 15.99 0.29 4.04 16.85 0.3 4.04 17.73 (table from Doc#843972)
Flood Warning Procedures Manual 2003 Page 71 Flood Procedures (Mangatangi River at SH2) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP L1 EMO Day, Night & Alert Modes 11.0 m Ring Mark Ball and advise him of Alarm message sent to the level and rainfall situation (Civil Defence Officer at Franklin DC). EMO 1 & 2 – Pager Ph 025 514 942. (no text messaging) Emergency Mgt Off – Email Note: At 11.6m, the river is very swift and this alarm setting gives Franklin DC – Faxes about 2 hours warning of possible (Ronnie Gram & Mark flooding. Ball)
Fully Activate HydroTel MAF - Fax L1 EMO 12.0 m As above Inform Franklin District Council of possible flooding (if level hits 12.3m).
Fully Activate HydroTel L1 EMO 13.0 m As above.
Fully Activate HydroTel L1 EMO 13.5 m As above, and
Approaching 1998 flood level of 13.56m.
Mangatangi River at SH2: Return Periods Flood Estimates For Mangatangi Stream Flood Return Period 2.3 Year 5 Year 10 Year 20 Year 50 Year 100Year Location (mean annual flood) Mangatangi 14 26 35 44 54 62 Dam Spillflow
Return Period (yrs) 2.33 5 10 20 50 100 Gauge Height (m) 12.88 13.16 13.23 13.27 13.33 - Discharge (m3/s-1) 77 118 151 182 223 254
Page 72 Doc # 761111
Mangatawhiri Catchment – Background Information The Mangatawhiri River has its headwaters in the eastern Hunua Ranges, in a southerly direction. It collects water from three main tributaries: • Pouraureroa Stream (27 km2) • Waipunga Stream (23 km2) • Pokeno Stream (16 km2)
The river discharges into the Waikato River north of Mercer. The total catchment area above this point is 184km2.
Upper Catchment
The catchment area above the dam is approximately 26km2, predominantly in indigenous forest, with a small area of exotic plantation forestry.
Dam to Mangatawhiri Gorge
Downstream of the Dam the river flows 20 km through the Mangatawhiri Gorge. At this point the river has a steep gradient and contains riffles, runs and pools, along with several waterfalls.
A weir is located 8 km below the dam, this is monitoring flow for Watercare services. A minimum flow of 150 l/s is maintained at this point. There are three significant tributaries between the dam and the weir, Acherson Stream, Horne Stream and Milnes Stream.
Gorge to SH2
After leaving the gorge the river drains pastoral and bush covered land. The widening valley giving way too considerable areas of flood plains adjacent to the main river channel. Downstream of Mangatawhiri township Pouraureroa Stream joins the river. Mangatawhiri River then flows under State Highway 2.
SH2 to confluence with Waikato River
Mangatawhiri River now flows through flat, low lying pastoral land. Approximately 6km of stop banking on either side of the main river channel protects the land under the Mangatawhiri River Drainage Scheme, which includes a network of flood gates and pumping stations. The scheme ends just upstream of State Highway 1. After flowing under State Highway 1 the river joins the Waikato River downstream of Mercer.
The catchment contains a wide variety of topography from rugged hill country, with a maximum elevation of 688m, down to low lying flat areas of peat wetlands both drained and undrained, with an elevation of just 20m. Approximately two-thirds of the catchment is in pastoral farming.
Mangatawhiri Drainage Scheme
The Mangatawhiri Drainage Scheme was constructed between 1975 and 1979 to protect 1300ha of former swamp and poorly drained flood plain from flooding. The scheme is part of the Lower Waikato Waipa Control scheme and was constructed by the former Franklin County Council. It consists of four separate compartments. An earlier audit has shown that there are a number of areas where the scheme stopbanks are vulnerable to failure under design flood conditions. The audit and subsequent report stemmed from concerns raised by local drainage committee members and Franklin District Council. The structural audit highlighted deficiencies including that a significant number of scheme stopbanks have either steeper side batters or narrower crest widths than specified in the original design. A significant amount of work is
Flood Warning Procedures Manual 2003 Page 73 required to bring these stopbanks up to design standard and one problem that has been identified with this task is the difficulty of sourcing suitable fill material.
Scheme Description
Compartment 1 This compartment is situated upstream of State Highway 2 and includes the Lake Mangamate ponding area. The ponding area is protected by stopbanks running along the right bank of the Mangatawhiri Stream and the left bank of the Pouareroa Stream and also incorporating a 400m long spillway on the Pouareroa stream immediately upstream of the Mangatawhiri River confluence. The spillway was designed to operate in floods greater then the 14% risk event to attenuate the peak flow of the 5% risk flood in the Mangataehiri River from 280 m3/s upstream of the spillway to 200m3/s at state highway 2 and thus reduce design peak flood level for compartments 2,3 and 4. Both sides of the Mangatawhiri River below Lyons Bridge are stopbanked. The left bank stopbank is currently overtopped in significant flood events and when this happens flow over State Highway 2 into Compartment 2 occurs. The Pouareroa Stream is stopbanked on both sides over a length of about 950m. An approximate 500m length of the right bank at the downstream end has been constructed privately (“The Pope property Stopbank”) and is not part of the scheme. This bank is unauthorised and does not provide any significant berm with between the toe of the bank and the stream.
Compartment 2
This compartment is located on the left bank of the Mangatawhiri Stream immediately downstream of State Highway 2. The stopbank is approximately 2100mlong and is designed to protect against a 5% risk flood.
Compartment 3
This compartment is located on the left bank of the Mangatawhiri Stream. The stopbank extends from the high ground dividing this compartment from compartment 2 at its upstream end to Ryburns Lagoon and thence it departs at right angles to the river running across to high ground in the south. The stopbank is approximately 3700m long and is designed to protect against a 5% risk flood.
Compartment 4
This compartment is located on the right bank of the Mangatawhiri Stream immediately downstream of State Highway 2 and the stopbank is continuous between State Highway 2 and Ryburns Lagoon. The stopbank is approximately 4900m long and is designed to protect against a 5%risk flood.
Contour Drain
The objective of the contour and hillwater cut off drains is to divert hill catchment runoff around the edge of Compartment 4 to Ryburns Lagoon. The hillwater cutoff and contour drains are prevented from spilling into Compartment 4 by a stopbank running along their left bank. This bank extends approximately 3300m upstream from Ryburns Lagoon. At the junction of the hill water cutoff drain and the contour drain is a low level stopbank, and spillway which is designed to divert flood water in the drain to a ponding area adjacent to the right bank of the drain. This spillway operates in events greater than the annual flood. The objective of this ponding system is to attenuate peak flows in the contour drain thus reducing the required height of the left bank contour drain stopbank.
Page 74 Doc # 761111
Original Design Standards
The original design for the scheme was generally based on protecting against a 5% risk flood within the main components. Lower standards of risk were adopted for the Compartment 1 ponding area and some elements of the contour drain system. Main stopbanks were designed with a 3 metre crest width, batters of 2 1/2 :1 and 3:1 for the river and land side of the stopbanks respectively. The contour drain banks were designed to a lower standard with crest widths of 1.8m and batters of 2:1 on each side. Design freeboard’s within the scheme varied between 0.45m and 0.15m. This variable freeboard was adopted because it was envisaged that the proposed Lower Mangatawhiri dam would reduce flood levels. This dam has never proceeded and is not likely to in the foreseeable future.
Franklin District Assets
Franklin District Council is responsible for the stopbanks, floodgates and pump stations within the Council'’ boundaries. The assets, which require immediate maintenance and/or renewal are the pump stations of the Mangatawhiri compartments 3 and 4 and the Miller Farlane compartment. These pumps were audited in June 2002 and the reports will be sent to the District Council for action. Renewal of the Contour Drain stopbank is required and should be undertaken during the summer season.
Flood Alarm Procedures
Watercare Services’ telemetry system will automatically notify the EMO 1 (by text message) when:
1. Dam level rises above 150mm below overflow:
Expected Message: "Mangatangi Dam Level 150mm below overflow and rising"
2. Dam level falls below 300mm below overflow:
Expected Message: "Mangatangi Dam Level 300mm below overflow and falling"
A check on the situation with Franklin DC is also advisable (contact details follow below).
Website Information
Lake level and percentage full data is now available on Watercare’s website (www.watercare.co.nz). This data is collected to manage the resource most effectively, and to indicate when the lakes might overflow, allowing more water into the downstream watercourses.
24 hrs Control Centre
7.30am – 4.00 pm: Ardmore Treatment Plant Ph (09) 292 8634 Peter Dopheide ([email protected])
Afterhours: Church Street Control Centre Ph (09) 634 7840 (Hunua Duty Officer)
Emergency Contacts
Gavin Palmer, Operations Manager, Water, ph 0274 845 556, [email protected].
Brian Park, Hunua Superintendent, ph 0274 938 212, [email protected].
Flood Warning Procedures Manual 2003 Page 75
Shayne Cunis, Process Engieer Waikato, ph 027 277 8618, [email protected].
Hydrological Characteristics of Mangatawhiri River Site Catchment Flood Flows (m3/s)3 Area (km2) MAF 5 year 10 year 100 year
Upper Dam 25.8 27 40 65 135
Lower Weir 44.3 62 95 140 260
Above 78.3 87 130 190 350 Pouraureroa Stm
SH2 105.7 83 120 150 250
Waikato 183.5 80 115 145 235 Confluence
Page 76 Doc # 761111
Upper Mangatawhiri Spillway Rating Curve H(m) C(ft units) Q(cumecs) 0.1 3.0 6.3 0.2 3.05 18.1 0.3 3.1 33.9 0.4 3.15 53.0 0.5 3.2 75.2 0.6 3.25 100.4 0.7 3.3 128.5 0.8 3.35 159.4 0.9 3.4 193.0 1.0 3.45 229.4 1.1 3.5 268.5 1.2 3.55 310.3 1.3 3.6 354.8 1.4 3.65 402.1 1.5 3.7 452.0 1.6 3.75 504.7 1.8 3.85 618.3 2.0 3.95 742.9 2.2 4.0 868.0 2.4 4.0 988.9 2.6 1070 2.8 1130 3.0 1180 3.2 1230 3.4 1280 3.6 1330 3.8 1370 4.0 1420 (Table from Doc#843972)
Flood Warning Procedures Manual 2003 Page 77 Upper Mangatawhiri Rating curve (0.01 – 0.30 m) H(m) C (feet units) Q (cumecs) 0.01 2.955 0.20 0.02 2.96 0.56 0.03 2.965 1.02 0.04 2.97 1.58 0.05 2.975 2.21 0.06 2.98 2.91 0.07 2.985 3.67 0.08 2.99 4.50 0.09 2.995 5.38 0.1 3 6.31 0.11 3.005 7.29 0.12 3.01 8.32 0.13 3.015 9.39 0.14 3.02 10.52 0.15 3.025 11.68 0.16 3.03 12.89 0.17 3.035 14.14 0.18 3.04 15.43 0.19 3.045 16.76 0.2 3.05 18.13 0.21 3.055 19.54 0.22 3.06 20.99 0.23 3.065 22.47 0.24 3.07 23.99 0.25 3.075 25.55 0.26 3.08 27.14 0.27 3.085 28.77 0.28 3.09 30.43 0.29 3.095 32.13 0.3 3.1 33.86 (Table from Doc#843972)
Page 78 Doc # 761111
- - - THIS SECTION IS UNDER DEVELOPMENT - - -
Lake Taupo Levels – Procedures Background The Taupo Control Gates regulate the flow of water down the Waikato River, allowing water to be stored in Lake Taupo and released down the river to meet electricity generation requirements of the Waikato Hydro System. Whilst the operation of the Taupo Control Gates has some influence eon lake levels, the levels are largely determined by inflows into Lake Taupo which at times can greatly exceed the 315 cumecs capacity of the outlet. There are about 30 major tributaries entering the lake with the Waikato River being the only outlet.
The working levels of the lake are summarised in the following diagram:
358.0
357.72 Maximum level recorded (October 1909) 357.5 357.39 357.25 357.0
356.5 NORMAL LAKE LEVEL RANGE (1.4 m)
356.0 355.85 Minimum Operating Level 355.70 Minimum Natural Level (July 1946) 355.5
Metres above sea level
Lake Taupo Flood and Erosion Risks
• Inundation from high lake levels, wave overtopping, and backwater effects on rivers
• Erosion of lakeshores due to wave action during high lake levels
• Restrictions on the use of jetties and boat ramps
• Exposure of community assets such as pathways, roads and storm water systems
• Increased water tables which affects septic tank and sewerage system operations
Due to the expiry of the Tongariro Offset Works Agreement (TOWA) and resource consent requirements, the following principles have been developed and will apply to
Flood Warning Procedures Manual 2003 Page 79 the operation and management of Lake Taupo levels (as taken from the High Flow Management Principles: i) The maximum working level as specified in the Lake Taupo Compensation Claims Act 1947 is 357.39 metres. The Taupo gates were designed and constructed for the purpose of controlling the waters of Lake Taupo within a range of levels, none of which exceeds the maximum working level. ii) The maximum control level for the lake is 357.25 metres. The Taupo gates will not be used to operate the lake above this level solely for power generation purposes. If lake levels exceed this level then table discharges shall apply (as per the flood rules) until the level of Lake Taupo returns to 357.25 metres unless: • Reduced outflows are required for dam safety reasons. • Otherwise lawfully directed by Environment Waikato for flood management or other emergency reasons. iii) The Taupo gates will be used to manage the level of Lake Taupo with the following management objectives: • A less than 20% annual exceedance probability of 357.25 metres (i.e. an average 1 in 5 year recurrence interval). • A less than 5% annual exceedance probability of 357.39 metres (i.e. an average 1 in 20 year recurrence interval). • A less than 1% annual exceedance probability of 357.50 metres (i.e. an average 1 in 100 year recurrence interval). iv) Flood conditions will be deemed to exist in Lake Taupo when Lake Taupo levels are above the maximum control level of 357.25 metres asl.
The Flood Rules
Phase 1
Phase 1 of the flood rules is primarily a warning phase. Phase 1 may be entered into by agreement and provides for some pre-emptive measures to be undertaken in advance of heavy rain warnings and after consideration of the following criteria:
• Catchment wetness (API). • Elevated water levels: • Lake Taupo (> 357.00 metres). • Waikato River (> 650 m3/s at Ngaruawahia). • Tributary inflows. • Risk profiling for lake Taupo shows >5% probability of exceeding 357.39 metres within a 3-week timeframe.
Page 80 Doc # 761111
• Risk profiling for Lake Taupo shows >1% probability of exceeding 357.50 metres within a 3-week timeframe. • An assessment of flood risks.
Pre-emptive measures to be considered include:
• Draw down of reservoirs to create storage (including spill if deemed necessary). • Manipulation of flows to affect the timing of flood peaks.
Phase 2
Phase 2 of the flood rules provides for actions to be taken during heavy rain or flood events to limit the effects of flooding. Phase 2 shall be entered following an overall assessment of flood risks that takes account of the following matters:
• Lake Taupo level relative to the maximum control level (357.25 metres); • Waikato River flow at Ngaruawahia relative to a reference level of 850 m3/s flow at Ngaruawahia; • Catchment inflows that cause or seem likely to cause the hydro reservoirs to rise above maximum control levels; • Catchment wetness (API).
Actions to be taken in phase 2 following consultation with the parties include:
• Ceasing to divert TPD foreign water into Lake Taupo if the maximum control level for Lake Taupo (357.25 metres) has been reached. • Retaining water in Lake Taupo and/or the hydro lakes. • Draw down of reservoirs to create storage. • Manipulation of flows to affect the timing of flood peaks.
Alarm Notifications:
When Lake Taupo exceeds 357.00 metres an automatic email to all EMOs is generated as per the High Flow Management Plan Principles.
Flood Warning Procedures Manual 2003 Page 81 Tongariro River - Procedures Background Information The headwaters of the Tongariro River System consist of a complex array of streams that drain the eastern flanks of Mt Ruapehu. It is considered to have a very “flashy” nature and as such it poses a significant flood risk to the northeastern suburbs of Turangi. In response to this, stopbanks have been constructed both upstream and downstream of the SH1 Bridge.
The Tongariro River forms part of the Tongariro Power Development (TPD), which is a hydroelectric scheme based on diverted water from parts of the headwaters of the Whangaehu and Rangitikei Rivers (Eastern Diversion) and Whanganui River (Western Diversion). After being used for electricity generation by the Rangipo and/or Tokaanu Power Stations, the water ends up in Lake Taupo.
Further information can be obtained from the “Lower Waikato Waipa Control Scheme Asset Management Plan 1997”.
Operating Criteria: Genesis Power is to notify Environment Waikato when sluicing is planned at the Rangipo Power Station (this causes rapid increases in suspended sediment (ash) in the Tongariro River).
The Rangipo sluice gate will be opened to flush out the settling basin during times of high river flows (>100 cumecs). During intervals when flows are not considered adequate to flush the sediment through the system, the gate will remain closed.
Diversion of water from the Tongariro River into Lake Rotoaira (via the Poutu Intake/Canal) must cease when Turbidity units exceed 40 NTU’s. When this occurs, an alarm will be promulgated out via the flood warning paging network. The onus, however, remains with Genesis to ensure they close the Poutu Intake gates under these conditions.
Refer diagram below for specific flood warning procedures. Note: Genesis’s Scada Alarms are not triggered until 250 cumecs is exceeded.
Page 82 Doc # 761111
EMO pager will be activated when flows at Poutu Intake exceed 200 cumecs.
Return Period Flood Estimates
Return Period (yrs) Flood Peak (m3/s) Flood Peak (m3/s) (T & T 1997) (T & T 2003) 2.3 420 440 5 540 590 10 720 770 20 900 930 50 1200 1150 100 1400 1300 200 1550 1450 500 1800 1650
Flood Warning Procedures Manual 2003 Page 83 Overview of the Lake Taupo System
Aratiatia Dam
Control Gates Waitahanui River Taupo Kinloch Hinemaiaia Stream
Lake Taupo Waitetoko Stream
Kuratau River
Tauranga-Taupo River TPD Turangi
Tongariro River Waimarino River
Lake Rotoaira Poutu Canal
X Rangipo Dam
Waipakihi River Western Diversion
Waikato Stream Mount Ruapehu Tunnel
Eastern Diversion Moawhango Lake
Page 84 Doc # 761111
Why provide Flood Warnings?
Environment Waikato provides flood warnings for this river system because:
1. The Tongariro River is a major system flowing through highly developed areas 2. Areas inside and outside the flood protection area are becoming further developed, hence more people require warnings 3. Its “track record” suggests that it is prone to severe floods (although the risk has been significantly reduced since the completion of the protection scheme and the upstream draw-off by Genesis). 4. Potential impacts include the closure of major transport links (SH1) and the isolation of the northeastern suburb of Turangi. 5. It provides vital information and assurance for the local Civil Defence organisations during major events.
Telemetered flood warning stations related to this river system are:
Rainfall: Tauranga-Taupo Catchment @ Kiko Rd
Water Level: Tongariro River @ Poutu Intake Flood Procedures (Tongariro River at Poutu Intake) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP L1 EMO Day, Night & Alert Modes Routine monitoring. 2.4 m Alarm message sent to Fully Activate HydroTel EMO 1 & 2 – Pager L1 EMO Emergency Mgt Off – Email 4.0 m Taupo LO – Pager Approaching 1998 flood level of 4.36m. Genesis (Tokaanu Ops) – See chart below for contact information. Fax Taupo DC – Email & Fax
Flood Warning Procedures Manual 2003 Page 85 Tongariro River (below Poutu Intake) Flood Warning Procedures
High Flows and Scada Alarms Impending Flood Downstream of Poutu Intake >250 cumecs ↓ Environment Waikato Genesis contacts Environment Waikato EMO Ph: (07) 856 7184 work 025 992 120 mobile Genesis Flow Fax:(07) 856 0551 Phone 07 386 8113 Councillors: Helen Lane Ph(07) 333 9334 Fax(07) 333 9334 Laurie Burdett Ph (07) 378 3025 ↓ Environment Waikato Taupo District Council Contacts Taupo DC John Campbell Ph: (07) 386 7017 work (07) 386 8251 private 025 430 307 cell Fax: (07) 386 8449
Mike Keys Ph: (07) 377 9826 work (07) 378 4415 private 025 940 125 cell Fax: (07) 378 0118 ↓ Taupo DC contacts Landowners, Transit NZ
N.B. The flood warning procedures above are provisional until further consultation with Genesis and TDC takes place.
Page 86 Doc # 761111
Tauranga-Taupo River – Procedures
Background Information The Tauranga-Taupo River drains part of the western slopes of the Kaimanawa Ranges, and is considered to be one of the four quickest responding rivers in the region. Specific information regarding the behaviour and dynamics of this river system is scarce. It enters Lake Taupo at Oruatua (located on the eastern shores of lake).
Why provide Flood Warnings?
Environment Waikato provides flood warnings for this river system because:
1. The Tauranga-Taupo River is considered a flashy river system flowing through productive land
2. Its “track record” suggests that it is prone to severe floods
3. Potential impacts include the closure of major transport links (SH1) and the inundation of an exotic forest block
4. It provides vital information and assurance for the local Civil Defence organisations during major events.
Telemetered flood warning stations related to this river system are:
Rainfall: Tauranga-Taupo @ Kiko Road
Water Level: Tauranga-Taupo River @ Te Kono
Flood Warning Procedures Manual 2003 Page 87 Flood Procedures (Tauranga-Taupo at Te Kono) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP L1 EMO Day, Night & Alert Modes Contact Taupo District Council. 1.2 m Refer next page for contact details. Alarm message sent to
Contact Graham Taylor if 150 EMO 1 & 2 – Pager cumecs is likely. Emergency Mgt Off – Email Taupo LO – Pager Councillors – Fax Taupo DC – Email & Fax MAF – Email & Fax Opus – Email & Fax Forest Managers – Fax Fulton Hogan – Pager & Fax Fully Activate HydroTel Day, Night & Alert Modes L1 EMO 1.75 m As above…but contact Alarm message sent to OPUS International to advise that the SH1 Bridge and the EMO 1 & 2 – Pager adjoining sections of SH 1 look likely to be inundated (> 1.800 Emergency Mgt Off – Email m). See next page for contact details. Taupo LO – Pager
A “courtesy” call is also made to Councillors – Fax the NZ Forest Manager as sections of their plantations are Taupo DC – Email & Fax prone to overland flow during these flood conditions (see table MAF – Email & Fax below for contact details). Opus – Email & Fax Fully Activate HydroTel L1 EMO Forest Managers – Fax 2.25 m Inform Taupo District Council of Fulton Hogan – Pager & possible Orauanui flooding on Fax the eastern shores of Lake Taupo.
Approaching 1998 flood level of 2.67m.
Page 88 Doc # 761111
Kiko Culvert Operation (Tonkin & Taylor Report 2002) A key part of the overall scheme is the Kiko culvert which has recently been upgraded (2003). Twin box culverts of 1.5m by 1.5m have been constructed to supplement the existing capacity provided by twin 1.2 m diameter culverts. Without spilling across the state highway, the previous culvert had a capacity of approximately 8m3/s, while the total capacity of the new culverts will be about 22m3/s.
A separate flow routing model was used to evaluate the hydraulic effects of increasing the culvert capacity. Essentially, installation of the new culverts will have the following benefits:
• Spilling across the state highway would occur less frequently, i.e. for floods greater than a mean annual event (150 m3/s at Te Kono, return period 2.3 years), rather than about 100m3/s currently, a flow which would be exceeded typically one or more times each year.
• The ponding area would be smaller, and duration of ponding would be shorter, given the same magnitude flood in the river; ponding duration’s would typically be 12 hours shorter, e.g. in the 50 year design flood, the ponding duration would reduce to about 28 hours from 41 hours currently.
Contact Numbers Contact Number Comment Taupo District Council John Campbell 025 430 307 Mobile To advise landowners or (07) 386 7017 work Graham Pilet (07) 386 8251 private 025 294 7138 (07) 386 8449 fax Martin Sears 0274 930 557 Civil Defence Officer Mike Keys 025 940 125 Mobile (07) 377 9826 work (07) 378 4415 private (07) 378 0118 fax OPUS International (07) 378 0746 Road conditions/closure Consultants - Taupo 025 974 587 Richard Cave or Nick Gurr NZ Forest Manager (07) 386 8757 flooding of forests Chas Hutton (07) 386 7020 (courtesy call) Fulton Hogan – Taupo (07) 377 2274 - work Road conditions/closure for Dennis Hancock (07) 377 3047 - fax Turangi area 026 368 2559 pager Graham Taylor (07) 386 5406 - home Call if 150 cumecs likely (025) 246 6553 - mob (07) 386 6125 - fax Warwick and Bernadette (07) 386 7442 - home SH1 Te Rangiita Horton Mike Burns (07) 386 8234 – work? Challenge Service Station
Regional Councillors: Helen Lane (07) 333 9334 (ph/fax) Lauri Burdett (07) 378 3025
Flood Warning Procedures Manual 2003 Page 89 Return periods as derived by Tonkin and Taylor (As per the Tauranga-Taupo River Flood Risk Management Scheme Assessment of Environment Effect Report dated September 2002)
Flow Distribution For a Range of Flood Sizes for the Preferred Option Flood Return Period (Years) Flow at Key Locations 2.3 (Mean 5 10 20 50 100 200 Annual Flood) Flow at Te Kono (m3/s) 150 197 235 271 318 353 388 Overflow into Quarry 0 0 1.5 11 30 45 62 (m3/s) Kiko Overflow 23 45 60 72 82 91 99
Te Rangiita Overflow 0 0 0 0 4 12 20 (m3/s) Flow Under SH1 Bridge 125 146 164 175 205 232 256 (m3/s)
Page 90 Doc # 761111
Awakino River - Procedures
Background Information The Awakino River is a major river system. Its headwaters are located in the Herangi Ranges southeast of Marakopa on the Western Seaboard. The Awakino River is well- known for its scenic passage through the Awakino Gorge (the “corridor” to New Plymouth) adjacent to SH3. The river then flows SW entering the Tasman Sea at Awakino.
The lower reaches of the Awakino River are tidal, to calculate the high and low tides this Niwa site can be used, http://www.niwa.co.nz/services/tides.
Why provide Flood Warnings?
Environment Waikato provides flood warnings for this river system because:
1. The Awakino River is considered to be a major river system flowing through highly intensified land 2. Its “track record” suggests that it has produced severe floods 3. Potential impacts include the closure of major transport links (SH3) 4. Many of the lower river berms are grazed and farmers need timely warnings to move stock 5. It provides vital information and assurance for the local Civil Defence organisation and roading contractors during major events.
Telemetered flood warning stations related to this river system are:
Rainfall: Awakino Catchment @ Waitanguru
Water Level: Awakino River @ SH3 Flood Procedures (Awakino River at SH3) Alarm Return Actions Required by EMO HydroTel Status and Level Period Actions & AEP L1 EMO Day, Night & Alert Modes 3.0 m Routine monitoring. Alarm message sent to EMO 1 & 2 – Pager Emergency Mgt Off – Email Landowners (M Black, R Black & M Hammond) - Fax MAF – Email & Fax Waitomo DC –Fax Transfield Main – Fax Waitomo Civil Con – Fax NIWA-Hamilton - Email
Flood Warning Procedures Manual 2003 Page 91 Fully Activate HydroTel Day, Night & Alert Modes L1 EMO 3.80 m Alarm message sent to Contact Transfield Maintenance and Waitomo EMO 1 & 2 – Pager District Council of possible road closure (SH3) based Emergency Mgt Off – Email on current rate of rise and weather forecast (see Landowners (M Black, R MetConnect, Page 94). Black & M Hammond) – Fax See next page for contact details. MAF – Email & Fax
Fully Activate HydroTel Waitomo DC –Fax L1 EMO 4.6 m As above… Transfield Maint – Fax
Fully Activate HydroTel Waitomo Civil Con – Fax L1 EMO 5.5 m NIWA-Hamilton - Email As above…and advise that
SH3 through the Gorge is likely to be inundated and should be closed by this point. Current level is approaching the 1998 flood level of 5.75m. Ladies Mile becomes inundated at this point (especially if the tide is high). For the record, the maximum level recorded is 7.008 m on 8/6/88 @ 1230 hrs.
Transfield Emergency Contact
Transfield, who are responsible for some of the State Highway road maintenance in the region, now have a 24hr duty officer, whose number is:
Ph 07 848 0055 Fax 07 848 0050
Routine contact can be made with Mike Manion (025) 849 297.
Transfield should be advised of any relevant impacts from flooding etc that we are aware of and are responsible for the following road maintenance:
SH3 – Hamilton to New Plymouth SH4 – Taumarunui to SH3 SH36 - Te Kuiti to Managkino SH37 SH3 to Waitomo SH31 Otorohanga to Kawhia SH39 SH31 to Whatawhata
Page 92 Doc # 761111
Other Contact Details Road Conditions:
Waitomo District Council Ph: 07 878 8801 Fax: 07 878 771 Waitara Police Ph 06 754 8888
The level of the river at which the road becomes inundated is yet to be fully defined, but its believed that the Bailey Bridge goes under when the level exceeds about 5.75 m. Areas such as the “Ladies Mile” becomes inundated at this point too. At 5.5m road in Gorge can be inundated Awakino River at SH3: Return Periods
Return Period (yrs) 2.33 5 10 20 50 100 Gauge Height (m) 4.68 5.32 5.8 6.3 6.85 7.3 Discharge (m3/s-1) 200 260 310 360 420 470
Flood Warning Procedures Manual 2003 Page 93 Coastal Flooding - Procedures
Firth of Thames Coastline Warnings of potential coastal flood events on the Firth of Thames originate from Environment Waikato’s multi-sensored Thames Tide Gauge (Tararu) located 400 m offshore from the Thames suburb of Moanatairi. The MetService also issues tailored warnings for storm surge potential for the Thames coastal area (refer section below).
The Thames site records the following information:
Sensor Type Measured Units Comment Wind Speed km/hr 5 minute average Wind Direction degrees 5 minute average Barometric Pressure hectopascals (HPa) 5 minute average Tide Level metres (m) Influenced by lunar/solar cycles, and storm surge components Wave Amplitude metres (m) max-min wave height over 5 minute average
The Niwa site has a tide forecaster that gives the date, time and height data of tides. Where coastal areas and rivers are influenced by tides this information may be helpful, in providing a time at which the flood level will peak. http://www.niwa.co.nz/services/tides MetService Warnings for Abnormally High Sea Water MetService currently provides an advisory service by issuing advanced warnings (see example below) on the likelihood of abnormally high sea water for the Firth of Thames. These are based on the occurrence of particularly high tides in combination with high sea waves and swell, low atmospheric pressure, and strong onshore winds.
Please note that providing accurate storm surge warnings is not an easy task owing to the differing topography of the sea bed from one part of the coast to another and the lack of real time data for sea levels. MetService are therefore not in a position to provide reliable quantitative estimates of water height (the NIWA designed storm surge model will provide this data more accurately – refer section below).
As such, this service is on trial for 12 months beginning 1 August 1997. An evaluation will then be undertaken by the MetService (in consultation with the end-users) to gauge the accuracy, reliability, and effectiveness of the service. If it proves to be a valuable service, it will then be updated and re-instated.
Typical Storm Surge Indicators When any alarm is received from the Thames Tide Recorder or if MetService issue a Special Advisory for high sea levels, the Level 1 EMO should become more proactive in monitoring the weather/sea conditions on the Firth of Thames.
The potential for storm surge activity depends upon the state of the tide (i.e. storm surge risk is obviously drastically reduced during low-mid tide). The Level 1 EMO can access the predicted tide levels in HydroTel (up to year 2005).
The key indicators for which the Level 1 EMO should watch out for are: Note: these are recommended settings only (i.e. they are not the result of modelling).
Page 94 Doc # 761111
1. Predicted Peak High Tide : generally between 1.80 and 2.50 metres 2. N-NW Winds : > 25 km/hr 3. Wave Amplitude : > 1-2.00 m 4. Barometric Pressure : < 1000 HPa
Please note that these parameters act individually from each other, and that under certain conditions, their contribution to peak storm surge levels can vary remarkedly. Alarm Settings and Promulgation The current alarm settings on the Thames Tide Recorder are:
1. Wind Speed: : @ 60 / 80 km/hr
2. Barometric Pressure: : < 1000 Hpa
3. Tide Level : 2.05 m
Note: these alarm settings are provisional (i.e. they have not been based on any scientific formula for storm surge forecasting).
Alarms are promulgated automatically from the telemetry system via the pager and faxing network. Current receivers include Thames-Coromandel District Council, Franklin District Council, Hauraki District Council, and Manukau City Council. Contact Details Although the following external contacts receive alarms directly from the Thames Recorder site via the HydroTel network, the necessity to contact them directly (by phone) really depends on the current conditions and the magnitude of the predicted/expected event. The Level 1 EMO will need to regularly monitor the high tide levels and their times. Running the NIWA model will help facilitate this more effectively. However, the Level 1 EMO has the option to request appropriate internal staff (including afterhours) to come into the office to activate and run the model.
Contact Organisation Number Comment Ron White Thames-Coromandel DC (07) 868 9586 potential warnings (CDO) Cell: 0274 981 871 for Thames / Pager: 026 246 2655 Tararu Ian McLeod Hauraki DC (07) 862 8609 potential warnings (Engineer) Cell: 025 819 008 for Waitakaruru Thames Mark Ball Franklin DC (09) 238 6349 potential warnings (CDO) Cell: 025 514 942 for the Kaiaua area A/h (09) 238 6995 Judy Fowler Manukau City Council (09) 262 8900 potential warnings (CDO) Pager: 026 367 5673 for Kawakawa Bay A/h (09) 576 7325
Tidal Constituents and Definitions 1. Spring Tide: when the sun, moon, and earth are aligned (new and full moon)
2. Neap Tide: when the moon is at right angles to the sun-earth axis Spring and neap tides occur approximately every two weeks.
Flood Warning Procedures Manual 2003 Page 95 3. Perigee Tide: when the distance between the earth and moon is closest The perigee tides occur approximately every 55 days. If the perigee coincides with a spring tide (roughly every seven months), the tidal peak height will be enhanced.
Tararu Storm Surge Forecasting Model Model Designer: NIWA PO Box 8602 Christchurch Ph: (03) 348 8987 Fax: (03) 348 5548
Attn: Glenn Carter and/or Jane Hill e-mail: [email protected]
Model Support (Trouble-Shooting):
All queries regarding the operation/activation of this model should be directed to:
Adam Munro ext 8944 Ph: (07) 853 8823 (a/h) should he be unavailable, contact:
Ross Jones ext 8714 Ph: (07) 854 9245 (a/h)
Background Information
This program has been designed to predict sea levels at Tararu up to 60 hours in advance. However, based on the statistical confidence intervals, it is recommended that the results are best interpreted within 20 hours. This is achieved using a neural network (i.e. it is able to use past events to modify predictions) which has been trained on two years worth of data which are representative of typical conditions in the region. In order to run the program, it is necessary to have a Tideda (or Hydrol) data file holding recorded sea level data for at least eight days prior to the time at which the forecasts are required.
Real-time Forecasting On start-up, the program enters real-time forecasting mode (Real Time), picking up the current data and time from the system clock (it has been adjusted for daylight saving). The required sea level data is retrieved from the Tideda file and is used to predict sea- levels up to 60 hours ahead.
The main display shows two plots, the top one (refer picture over page) shows the calculated astronomical tidal component for the last week, and for the next 60 hours. The tidal component is depicted by a blue line. The bottom plot shows recorded sea level data for the last week and predicted levels for the following 60 hours. The recorded data is displayed by a black line and forecast data are shown by a red dotted line. The green vertical line in both plots show the system clock time at startup or the time interactively by the user.
Also indicated are the times of full moons, new moons, and perigees (when distance between the earth and moon is shortest).
Demonstration Mode Forecasting By entering this mode (Demo), the user can see what the program would have predicted for previous data, and compare it to the actual recorded sea levels. The user
Page 96 Doc # 761111
may scroll through the data one day at a time using the arrow buttons on the lower left of the screen, or choose a specified date and time using the Change Date button.
Listing Data The recorded and forecast data can be listed by pressing the List Data button. These may be listed either as peaks and troughs, or as hourly values. The options panel is used to set whether extrema or hourly values are displayed. If hourly values are chosen, then the range of values to display can also be set. Statistics can be viewed by pressing the Statistics button.
Statistics Summary statistics were calculated using a test set of data for which recorded data were available. Errors were calculated as the differences between recorded peaks and troughs and predicted peaks and troughs. For the test period, the minimums, maximums, means and standard deviations of errors are given, along with 95% confidence intervals. These are displayed for peaks, troughs, and for both peaks and troughs combined.
Options The options panel allows the users to specify the location of the recorded data. This is achieved by setting the file name and path as well as the site and item numbers.
Installation The following files make up the total package of the model. They must be stored in the same directory:
storm.exe stormf.dll tilib32.dll thames1.cns moon1.csv
The following staff currently have the model installed on their PC’s:
Brendan Morris (ext 8948)
The initialisation file storm.ini will be created at startup if it doesn’t exist. Once created it must be kept in the same directory as the other files.
Flood Warning Procedures Manual 2003 Page 97
Waikato River at Hoods Landing (Tide / River Gauge) An alarm of 2.2 metres has been set on this site (Alert only). Factors that will increase the risk of a significant storm surge event here will be strong (30-50 km/h) onshore winds from the south or southwest associated with large swells and low barometric pressure (<1000 hpa).
Two automatic weather stations (AWS), one located on the Manukau Harbour heads, the other at Port Taharoa, can offer vital information such as wind speed, wind direction, and barometric pressure. These can be found on the internet at: Brian’s Weather Links: http://ps.gen.nz/~windy/links.htm MetConnect: http://www.metra.co.nz/metconnect/index.jsp
Login Name: ewaikato
Login Password: r1verfl0w Whitianga Harbour Tide Gauge An alarm of 1.2 metres has been set on this site (Day, Night & Alert) Factors that will increase the risk of a significant storm surge event here will be strong (30-50 km/h) onshore easterly winds associated with large swells and low barometric pressure (<1000 hpa).
IPA:
Catchment Groupings of API Values (mm) Low Moderate High Extreme Kauaeranga -Coromandel 0-20 20-40 40-60 60+
Page 98 Doc # 761111
Appendix B
HydroTel Operation Modes
Day/Night/Alert Modes
Day Mode This is in effect between 7.30am - 5.30pm Monday to Friday (normal weeks). It is has also been calibrated for daylight saving as appropriate. Both L1 EMO and L2 EMO receive pager message. Night Mode This is in effect for all other times outside the Day Mode settings. This includes afterhours, Weekends and Public Holidays. Alert Mode When certain levels are reached, the system will (on alarm) automatically send out selected pager messages and faxes to external customers (e.g. DC’s, EW field offices, etc.) This mode will remain activated until manually cancelled by the L1 EMO.
Summary of Actions: The L1 and L2 EMO (Hamilton) upon receipt of any alarm should:
1. Make a note of the station(s) at which an alarm has occurred in the flood log (Appendix I – or use the blue forms). This is also logged within HydroTel for post event analysis.
2. Carry out actions as directed by the pager message. Please refer to the relevant catchment action plan (in this manual) for further details.
Note: In any case, contact between the flood team in Hamilton and the Hazard Liaison Officers based in Paeroa and Taupo must be maintained throughout the event.
Any alteration to the polling schedules must be authorised by the L1 EMO as this could compromise the updating of both the Site Summary, 0832 Infolines and EW’s website.
Flood Warning Procedures Manual 2003 Page 99
Appendix C
Telemetry System (HydroTelTM) Configurations Note: 1. For detailed information about the telemetry system, please refer to the “HydroTel User Guide located in Docs.
2. 2. The “Notes” button in HydrotelTM can also be used to provide convenient access to background information on each site. Specific actions will also be listed here for quick reference only.
The Telemetry and Flood Warning system has two major functions: a) Automatic collection of data on river levels and rainfall totals from recording stations. This information is currently collected by the Environmental Monitoring Unit at Environment Waikato. b) The triggering of alarms (and pager/fax/email messages etc) during events when certain conditions relating to river flow, and/or rainfall totals have been exceeded. Polling Times Under normal operating conditions, daily polling times (including the updating of both the Site Summary and 0832 Infolines) for all sites are:
AM 12.30am 3.30am 6.30am 9.30am
PM 12.30pm 3.30pm 6.30pm 9.30pm
Note: Times reported in NZST. Alarm Promulgation Please note that apart from the four key sites (i.e. Jefferis, Tauranga-Taupo, Smiths, and Karangahake) and the key indicator sites within each key catchment (Ngaruawahia, Otorohanga, Maukoro Landing, and Te Aroha) alarms will be generated when the first alarm level has been reached. Polling Times Under Flood Conditions Polling times for all primary catchment groups will automatically switch to hourly updates when the system reverts to Alert Mode.
When this situation exists, any HydroTel adjustment MUST be pre-approved by the L1 EMO. It is imperative this procedure is followed to ensure that Environment Waikato’s website and 0832 Infolines are regularly updated. Special Polling Times for ‘Flashy and Key Indicator Sites’ Unless the System is already in Alert Mode, when the first alarm (or above) is triggered from any of these sites, polling time intervals will be automatically increased to hourly. Faxes and emails will be automatically sent out when river levels reach there first alarm level, and when rainfall intensities exceed programmed amounts. Special 0832 and Environment Waikato’s Website Updates These will also be updated hourly when the above conditions are reached.
Flood Warning Procedures Manual 2003 Page 101 Appendix D
Media Releases
First Media Release Media Releases should commence at or above the 3rd alarm. The Level 1 Emergency Management Officer is responsible (as is the Group Manager Asset Management under Delegation) for authorising media releases. Other staff should not deal with media enquiries nor put out a written bulletin. The Level 1 Emergency Management Duty Officer may however authorise particular staff to provide information and advice to the Corporate Media Liaison Officer, and also liaise with the media on points of clarification.
Refer to previous media releases (search in Docs) for the type of information that should be conveyed.
Because the Level 1 EMO is acting in the role of flood manager as distinct from their normal role within Environment Waikato, they should be referred to as the Emergency Management Officer in all communications and media releases.
The media release will be prepared by the Corporate Media Liaison Officer and passed to the Level 1 EMO for confirmation, before being released through the Telecom Smartfax system (rapid dissemination within 20 minutes to all media).
The Corporate Media Liaison Officer should be kept informed of any changes in the flood situation, however localised. Media in these areas may have a special interest in a particular tributary or ponding zone in small areas. Purpose The main purpose of a media release is to issue flood warnings to the general public, while providing information on predicted peaks, rainfall amounts, and areas affected. It also gives contact details to the media on whom they should consult (namely the L1 EMO) for further information or advice.
An electronic copy of each new media release will be available via Environment Waikato‘s website.
Corporate Media Liaison Officer – Contact Details: Name Contact Details Comment Linda Thompson Ext 8782 Home: (07) 855 0025 Cell: (025) 942 691
Page 102 Doc # 761111
Appendix E
Flood Operations Centre (FOC)
Activation based on Flood Conditions Activation of the FOC (Waikato Room) by the Level 1 & 2 EMOs should commence when key alarm levels are reached on any major river system. In some cases, it may be prudent to open the centre earlier. This is at the discretion of the L1 EMO, but depending on the circumstance (i.e. affected catchment and weather forecast) it may not be necessary for the team to activate the FOC at this stage. Purpose The purpose of the FOC is to “centralise” our response effort so that all outputs (i.e. media releases, status reports, road closure information, etc) are consistent and effective. It also provides the team an atmosphere with little disruption.
The Waikato Room also serves as our Civil Defence HQ in an emergency, hence the room is already well equipped with peripheral computer/phone/fax/email ports that can be quickly activated to handle both incoming and outgoing communications. Procedures
Activating the Flood Operations Centre 1. Book the Waikato Room on Calendar. If there are any conflicting appointments notify the person who booked the room and explain the circumstances. 2. Contact all members of the flood warning team and email all other Hamilton- based staff advising that the room is being used as the Flood Operations Centre. Also notify Environment Waikato staff via an All-Staff email. 3. Re-locate one or more of the Asset Management Group’s HydroTel client computers to the centre. 4. Stationary supplies, fax machines (and paper), phones, and cords etc are all stored permanently in the Civil Defence Cupboard.
De-Activating the Flood Operations Centre 1. Return the HydroTel client PCs to their normal locations 2. Cancel the room booking on Calendar 3. Contact all members of the flood warning team and e-mail all other Hamilton-based staff advising that the Waikato Room is no longer being used as the Flood Operations Centre. 4. Ensure that all paperwork generated from the event is Filed to a stand alone file number (it will also need to be profiled in Docs).
Flood Warning Procedures Manual 2003 Page 103 Appendix F
Antecedent Precipitation Index The Antecedent Precipitation Index (API) is a mathematical parameter which is used to represent the drainage conditions of a catchment. The parameter shows the relationship between rainfall and the catchments capability to store the water. API has a cumulative nature hence its usefulness in flood warning procedures. It allows the catchment wetness to have a “memory” and to be a stable indication of the conditions. With a value such as API it is possible to predict what effect forecasted rain may have on the catchment and to evaluate the real possibility of a flood event.
MRP have used API for a number of years in relation to their Hydroelectric Power Scheme and they have incorporated it into the Waikato Flood Management Rules as a parameter for advancing to the mandatory Phase 3 Flood Routing. As the Waikato River System is a large component of the region it was thought that API applied to this area and the rest of the region would be a support to the existing flood warning procedures.
Three questions on API were investigated; 1. How does it work? 2. How much additional flood warning could it provide? 3. How feasible would it be to implement this system for Environment Waikato?
The starting point of the investigation was the report prepared for ECNZ in March 1994 by Works Consultancy Services. This report thoroughly documents the API system and has been consistently used as a comparison to other information.
API works on using the previous 24 hours rainfall as an indication of how wet the catchment is. The totalled rainfall is weighted as a measure of rainfall over the whole catchment. By adding the previous days API value to the weighted rainfall and multiplying the value by a decay rate a representation of what the catchments wetness is can be established. The decay rate gives the API its memory and stability. MRP use a decay rate of 0.9. This gives it high stability and a memory of about 30 days. At present the decay rate is 0.9. This was to create the required stability but adjustment may be needed once the trial has been completed. The formula which is used to calculate API is illustrated below:
APIt = 0.9 × (APIy × R) APIt = API calculated for today 0.9 = the decay rate of the catchment APIy = the API calculated for yesterday R = the weighted rainfall for the past 24 hours. This is weighted on the proportion of catchment of a river level site downstream against the area of the whole catchment.
Investigation into the feasibility of API began by contacting ECNZ (now MRP), Hamilton and Horace Freestone of Works Consultancy, Wellington. ECNZ offered to show me their setup within the control room in Hamilton. A meeting was held with Richard Smith and Sarah Knowles at ECNZ, Peachgrove road on 5 December 1996.
Horace Freestone of Works Consultancy, Wellington was helpful and suggested another system called RORB. This is a rainfall-runoff computer modelling programme that allows for quite accurate flood peak prediction. Mr Freestone suggested contracting the Manawatu-Wanganui Regional Council for whom they had recently installed the system. Mr Freestone al so sent some manuals for RORB but could not provide any additional information on the API without prior consent from ECNZ.
Page 104 Doc # 761111
To gather other information on the API the University of Waikato Library, Environment Waikato’s library and the Internet where used. The information found did not give a full indication of how API worked or how well. At this stage (1997) it appears as though API is a system that is not widely used in New Zealand.
ECNZ were very helpful as any improvements to the Flood Warning Service by Environment Waikato is beneficial to their resources. ECNZ has a much more advanced technology system than Environment Waikato but API is a system that does not require extremely advanced technology. This makes it a cost effective system with the only major financial input being staff time. This is because existing applications such as Excel spreadsheets can be used to calculate the API. The meeting with ECNZ gave the opportunity to observe the API as a working system and also to see their flood routing system, Hydrol 3. ECNZ provided documentation and computer files on how their system operated. This was a reference for which to base the API for Environment Waikato.
From the gathered information it seemed as though a single API could be calculated for the whole region. This worked by using representative rainfall sites from each catchment. The first problem is how to calculate the 1st API. The formula used is :
2 n APIy1 = R0 + (0.9 × R1) + (0.9 × R2 + …(0.9 × Rn)
APIy1 = antecedent rainfall for day 1 R0 = weighted rainfall on day 0 0.9 = decay rate Rn = weighted rainfall on n days before day 0 Subscripts 1,2…. = rainfall during days previous to day 1
With using this recursive formula how many days the previous API should be calculated to was unclear. A relationship needed to be established between the rainfall recorder and the downstream water level site in terms of travel time. This was difficult to calculate for the whole Waikato region as there are a number of different types of catchments with differing river systems. At this point it became apparent that an API value for the whole region would be a misrepresentation. To be more representative API needed to be calculated on a catchment basis so that the true situation in each catchment could be observed.
To be able to calculate the API by catchment I had to use the rainfall sites available and work out which of the downstream river level sites they fed into. The area of the water level site and the area of the whole catchment was found by requesting information from Environmental Data’s Inforeq system. The area information enabled the rainfall for that catchment to be weighted giving a representative situation of the rainfall experienced over that whole catchment.
Listed in Table 2 are the rainfall sites used for each catchment, the downstream river level site area and the area of the whole catchment. With this is the value by dividing the smaller river level catchment by the whole catchment area. This gives a proportion over which theoretically the rain is falling. It is not true representation but unless there are a very large number of rainfall sites throughout the catchment rainfall distribution cannot be accurately found. Also stated is the number of previous days total rainfall required for the calculation of the first API. The values were found by plotting the river level for an event, for most sites the September 1996 event was used because there was little rain after the main event so a large amount was able to leave the catchment as runoff. Once the river level had peaked during the event the number of days that it took for the catchment to regain its monthly average value for September was worked out. The steeper catchments have a faster runoff rate so hence the number of days required to calculate API previous is less than for a slow response catchment.
Flood Warning Procedures Manual 2001 Page 105 Table 1: Summary of API information for calculations Catchment & Downstream Sub- Catchment Rainfall Number of Rainfall Sites River Level catchment Area (km2) Weighted Days for Site Area (km2) by (R) Previous API Taupo Basin Tauranga- Acacia Bay 3430 3450 0.99 12 Taupo Western Seaboard Waitanguru Awakino 226 2480 0.09 6 Waipa Wharekiri Whatawhata 2826 3930 0.72 10 Ngaroma T Kuiti Otewa Lower Waikato Wharekiri Rangiriri 12421 16140 0.77 12 Ngaroma T Kuiti Otewa Piako-Waitoa Maungakawa Maukoro 1103 1700 0.65 6 Landing Waihou – Ohinemuri Kaimai Puke Bridge 1606 2140 0.75 6 Golden Cross Te Aroha Kauaeranga- Coromandel Wharekawa Smiths 230 1890 0.13 4 Pinnacles
Once the Previous API has been calculated the Current API value can be found. The layout of the calculation is formatted in an Excel spreadsheet. Flood Risk Index The setting up the Antecedent Precipitation Index lead to a further question of whether it would be possible to develop another index that had a word rather than a numerical interpretation. The idea of creating such an index would be for use in informing the public through the media of the present flood risk in their area. With these ideas on what the index could mean no other guidelines where set. It was suggested that the index be as simple as possible to remove confusion and to indicate the probability of a flood occurring. It was envisaged to be similar to the New Zealand Fire Services Fire Warning Index. Using the values created for API the index could group certain values to give an indication on the of risk. For example groupings of low, moderate, high and extreme.
With API values being widely different for each catchment the grouping of values for a Flood Risk Index (FRI) would be different for each catchment. Originally it was thought that the API trial would need to be completed to enable trends to be established. As there was sufficient time to investigate the ideas and the archive data available with the established formula for each catchments API, graphs of long term trends where found. Since the last 12 months has created a number of flooding events it was possible to use data from the beginning of January 1996 through until about the end of January 1997 (except for Taupo Basin which was from August 1996 through to January 1997). The graphed trends of when flooding events occurred and how the API mirrored the
Page 106 Doc # 761111
events could be seen. It was obvious from these graphs that API could have provided additional warning time. By following this method for all of the catchments it was possible to create parameters for a Flood Risk Index. The table below illustrates the parameters for each catchment. The public will only be issued with the word interpretation with the values being used internally by the Flood Duty Officer.
Table 2: Illustration of API value grouping to create the Flood Risk Index Catchment Groupings of API Values (mm) Low Moderate High Extreme Taupo Basin (µm) 0-200 200-500 500-800 800+ Western Seaboard 0-4 4-8 8-12 12+ Waipa 0-100 100-200 200-300 300+ Lower Waikato 0-100 100-200 200-300 300+ Piako-Waitoa 0-10 10-25 25-40 40+ Waihou- Ohinemuri 0-100 100-200 200-300 300+ Kauaeranga -Coromandel 0-20 20-40 40-60 60+
Flood Warning Procedures Manual 2001 Page 107 Appendix G
Metservice Information
Severe Weather Warnings (SWW) MetService SWW’s consist of both Watches and Warnings.
Watches are disseminated to all regional councils by the MetService at a relatively early stage, typically 24 hours ahead of the forecast event, or on the eve of a weekend or public holiday. They are not released to the media.
In comparison, Warnings are disseminated by the MetService to the media and District Councils. In general, warnings have a higher probability of the predicted event occurring.
SWW’s are released via faxes, pager messages, emails, and it is also available on the internet at MetConnect. ‘Hard copies’ (as a back up) should be circulated by records as soon as practical to the following staff:
- Incumbent EMO 1 - Dennis Crequer (for Couer Gold) - Scott Fowlds (Asset Management Group Manager) - Te Aroha Fax (07) 884 7893
MetService Contact Details Name Contact Details Comment
Severe (04) 470 0783 Internet Address Weather/Mesoscale MetConnect Forecaster (next page for login details) Lead Forecaster (04) 470 0794 Marine Forecaster (04) 470 0760 Rod Stainer Ph: (04) 470 0744 Email: National Forecasting Fax: (04) 473 5231 [email protected] Centre Manager
SWWs should be placed on File 30 80 05
Page 108 Doc # 761111
MetConnect
Weather information is now available online to all EW Staff.
This is a one stop shop for regional / mountain / lake forecasts, radar images & observations for the Waikato Region.
You can use this at work or at home because you will have the same login & password.
Under no circumstances is the login & password to be passed onto persons who are not staff members / councillors @ Environment Waikato. This requirement is part of our written contract with MetService.
There is also a 50 login limit @ any one time so if you find you cannot get on to the service then it is likely there are already 50 staff using it. However, in flood events the EMO team will have first priority.
There is also a 30 minute time limit for each session and information for some parts of the service is updated hourly.
It will be up to each person to login & check forecasts / observations for themselves when they need to.
Login is: ewaikato.
Password is: r1verfl0w (note the use of numbers for r1verfl0w not riverflow)
The site address is: http://www.metra.co.nz/metconnect/index
Flood Warning Procedures Manual 2001 Page 109 Appendix H
0832 River Level & Rainfall Infolines Infocall is a Telecom service that provides recorded information to customers 24 hours a day. It was established to provide provisional river level and rainfall information to customers (especially field staff), and to ease the amount of enquires to both the Emergency Management Duty Officer and the Freephone Operator. The information is updated automatically at the completion of a scheduled poll, usually every three hours (i.e. 6am, 9am, 12pm, etc) or hourly during an event (i.e. when the system is in alert mode).
Level 1 EMO Cell: 025 992 120 Pager: 026 262 6175
System Supervisor Work: (07) 856 0555 Ext 8714 A/H: (07) 854 9245 Cell: (025) 272 0078
In extreme cases:
IQuest Ph: (07) 849 8256 or Pager 026 252 8869
Telecom: Dial 126 (as a last resort)
Page 110 Doc # 761111
Appendix I
Flood Logs These must be completed and maintained by the Level 1 EMO when: • Any major alarm level is exceeded or when flood warnings are issued • Advice or instructions are given or any actions taken • Incoming calls are received If point 1 applies • All outgoing calls made When river levels return to normal, or upon completion of the Post Event Review, the Flood Log should be typed into an electronic document and profiled in DOCS – referencing it to 30 08 05.
A master copy is provided on the following page for convenience. Copies should be photocopied as required. The renowned “Blue Forms” which are labelled “Waikato Regional Council – Flood Data Logs” can also be used.
Flood Warning Procedures Manual 2001 Page 111 Flood Data Log
File No: 30 08 05 Page No:
Date: Recording Officer:
TIME SOURCE/ INFORMATION REMARKS DESTINATION
Summary of Situation as at:
Page 112 Doc # 761111
Appendix J
Post-Event Review and Operational Improvements Emergency Management Australia (1995) provides useful guidelines on post-event reviews. Reference should also be made to Munro et al. (1998) for an example of reporting, and to the output report of the regional flood hazard identification study for any particular aspects of flood hazard that should be discussed in detail.
All suggestions for operational improvements should be reported to the Level 1 Emergency Management Officer. The Level 1 EMO should compile a list of these suggestions and forward this to the Natural Hazards/Emergency Management Programme Manager at the end of each roster period. Criteria: Documentation procedures commence when key alarm levels are reached. Hence, all information gathered, logs, other documentation etc, must be placed on the relevant file (generally 30 08 05) and profiled in Docs. In large flood events, a specific file number should be established.
Flood events that result in significant impacts will require a post-event review involving all members of the response team, co-ordinated by the L1 EMO with guidance from the Group Manager, Asset Management. This is to ensure that all problems/concerns are identified, reported, and if necessary corrected. It is also a useful tool to provide feedback on the general response effort. An output report should then be produced summarising the event, followed by a presentation to the next Operations Committee.
Note: The Asset Management Group Manager may request the EMO 1 to produce a summary for the Operations Committee on any “flood” event.
For severe events, a comprehensive programme of additional data gathering and reporting should be undertaken (e.g. see Munro et al, 1998). These events must be fully documented and consequently filed.
Flood Warning Procedures Manual 2001 Page 113 Appendix K
SYSTEM SUPPORT All system (HydroTel) problems and requests for technical assistance should be directed to the System Supervisor and to the Level 1 EMO. Iquest (NZ) Ltd are contracted by Environment Waikato to provide system support outside normal office hours (also refer the Duty Roster for full contact details).
Role Contact Contact Details Telemetry System Ross Jones Ext 8714 Supervisor Ph: (07) 854 9245 (a/h) Cell: (025) 272 0078 IQuest Mike Cook Ph: (07) 849 8256 (work) or 07 957 8160 Pager: 026 252 8869 Cell: 021 763 953 (email [email protected])
Note: Environment Waikato has a system support agreement with IQuest, and as afterhour call-outs bear an associated cost, any such call-out are at the discretion of the Level 1 EMO or Programme Manager Environmental Data (Jim Price) in consultation with the Level 1 EMO. Hence, they must be fully authorised.
If available, the System Supervisor should also be contacted in the first instance.
Page 114 Doc # 761111
Appendix L
Performance Measures For Flood Warning The flood warning service is an intricate part of the Natural Hazards Programme. It is one of our core activities that help us to minimise the impacts of a natural hazard event at both the community and regional scale. Target Outcomes That our customers take appropriate actions based on the information provided by this service so that;
• There are no injuries or deaths (including stock) • There are no major commercial losses • There are minimal insurance claims • There are minimum net community costs, and • There are minimum environmental costs arising from flood events in the Waikato Region. Customer Focus Information will be provided;
• In a form that meets our customers needs • At a scale appropriate to our customer’s use • In time for our customers to take effective action
Flood Warning Procedures Manual 2001 Page 115 Appendix M
Supporting Information
Contents:
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
Page 116 Doc # 761111
Bibliography
General The Waikato Region Civil Defence Plan, 1999
Standard Operating Procedures for the Waikato Region Civil Defence Plan, 1999
Emergency Management Australia, 1995. Flood Warning, An Australian Guide.
Craigie, E, 1997. Flood Warning Service. University of Waikato Placement Report.
Williams, M.B., 1997. Environmental Data Report 1996, Environment Waikato Technical Report 1997/7.
Palmer, G.N., 1996. Review of the Environment Waikato Flood Warning Service. Environment Waikato Technical Report 1996/6.
*Check also against flood study bibliography* Taupo Basin Mulholland, M., 1993. Taupo Basin Strategy - Technical Report, Environment Waikato Memorandum, 15 March 1993, File 22 05 20.
Waikato Regional Council, 1992. Flood Emergency Procedures Manual (Waikato Catchments and Western Seaboard), Technical Report 1987/26, Revised June 1992.
Works Consultancy Services Ltd, 1990. Waikato River Power Development, Flood Management Rules, Specification HD 1080A., Revised August 1990, Wellington.
Works Consultancy Services Ltd and Environment Waikato, 1995. Kiko Farm Flood Protection, Preliminary Scheme Assessment.
Western Seaboard Waikato Regional Council, 1992. Flood Emergency Procedures Manual (Waikato Catchments and Western Seaboard), Technical Report 1987/26, Revised June 1992.
Waipa Environment Waikato, 1997. Lower Waikato Waipa Control Scheme Asset Management Plan 1997, Vol 1 & 2. Environment Waikato Policy Series 97/33
Waikato Regional Council, 1992. Flood Emergency Procedures Manual (Waikato Catchments and Western Seaboard), Technical Report 1987/26, Revised June 1992.
Waikato Regional Council, 1993. Te Awamutu Flood Management Plan, Technical Publication 93/10.
Flood Warning Procedures Manual 2001 Page 117 Lower Waikato
Barnett Consultants Ltd, 1994. Waikato River Morphological Model Study, Report on an Investigation Undertaken for Environment Waikato, Winstone Aggregates Ltd, Tuakau Sand Ltd, Hamilton.
Barnett, K., 1998 Flood Hazard Identification Report Waikato 1:50,000. Waikato Regional Council Technical Report IS98/01, Hamilton.
Freestone on Mangatangi July 1995
Environment Waikato, 1997. Lower Waikato Waipa Control Scheme Asset Management Plan 1997, Vol 1 & 2. Environment Waikato Policy Series 97/33
Munro, A. 1998. The Waikato regional flood event of 9-20 July 1998. Environment Waikato Technical Report 1998/15
Palmer, G.N., 1992. A Study of the Flooding Characteristics of the Mangatawhiri Drainage Scheme, Waikato Regional Council Technical Report 1992/20, Hamilton.
Palmer, G.N., 1996. The Effect of Vegetation on the Hydraulic Capacity of the Mangawara River - Hoe-O-Tainui to Jefferis Bridge, Environment Waikato Technical Report 1996/4, Hamilton East.
Parkin, D., G. Russell, M. Mulholland, G. Palmer, P. Mora, A. Munro and A.C. Poninghaus, 1995. Lower Waikato River, Report of Flood Event 17 July 1995, Final Report, Waikato Regional Council Technical Report 95/10.
Waikato Regional Council, 1992. Huntly Flood Management Plan, Technical Publication 1992/15.
Waikato Regional Council, 1992. Flood Emergency Procedures Manual (Waikato Catchments and Western Seaboard), Technical Report 1987/26, Revised June 1992.
Works Consultancy Services Ltd, 1991. Waikato River Power Development, Flood Management Rules, Specification HD 1080A., Revised August 1990, Wellington.
Works Consultancy Services Ltd, 1994. Waikato Power Development, API System, Wellington. Piako-Waitoa
Goring, D., 1995. Analysis of Tararu Sea Level Record, Consultancy Report No. EVW60501, National Institute of Water and Atmospheric Research.
Piako River Scheme Asset Management Plan 1997. Vol 1 main report. Environment Waikato Policy Series 1997/17 Waihou-Ohinemuri Environment Waikato, 1997. Waihou Valley Scheme Asset Management Plan 1997. Environment Waikato Policy Series 1997/17
Page 118 Doc # 761111
Goring, D., 1995. Analysis of Tararu Sea Level Record, Consultancy Report No. EVW60501, National Institute of Water and Atmospheric Research.
Palmer, G.N. and G.H. Walder, 1995. Hydraulic Modelling of the Lower Waihou and Ohinemuri Rivers, Draft Report, Environment Waikato Technical Report 1995/1.
Royds Consulting, 1995. Waihou Valley Scheme End of Scheme Review, Independent Review, Volume 3, Sub-Consultants Reports.
Kauaeranga-Coromandel
Dahm, J., 1986. Whitianga Marina Proposal, Hydrological Investigation, Volume 1, Flood Discharge Into Whitianga Harbour, Ministry of Works and Development, Hamilton.
Environment Waikato, 1997. Waihou Valley Scheme Asset Management Plan 1997. Environment Waikato Policy Series 1997/17
Environment Waikato, 1993. Te Puru Flood Management Plan, Technical Publication 1993/1.
Environment Waikato, 1995. Thames Flood Management Plan, Technical Publication 1995/4.
Goring, D., 1995. Analysis of Tararu Sea Level Record, Consultancy Report No. EVW60501, National Institute of Water and Atmospheric Research.
Palmer, G.N. and G.H. Walder, 1995. Hydraulic Modelling of the Lower Waihou and Ohinemuri Rivers, Draft Report, Environment Waikato Technical Report 1995/1.
Royds Consulting, 1995. Waihou Valley Scheme End of Scheme Review, Independent Review, Volume 3, Sub-Consultants Report
Flood Warning Procedures Manual 2001 Page 119