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  Services » Regional Services » River levels and rainfall » Flood event July/August 2008 » EW FLOOD EVENT SITREP 34

EW FLOOD EVENT SITREP 34

EVENT NAME: July 2008 storm event SITREP No: 34
Issued by: Environment Waikato Duty EMO1 Date/time: 10/8/08 09:00

Overview of storm event

The Environment Waikato (EW) emergency response team continues to monitor the Taupo, Waipa and Lower Waikato River catchments, as flood peaks continue to move through the systems. Scattered showers continue to fall across already saturated catchments, but are tending to reduce in scale and intensity.

Flood levels are falling in the Waipa system and lower reaches of the Waikato River. Levels on other rivers in the region are also falling. Rivers flowing into Lake Taupo have now receded, with the level of Lake Taupo also becoming steady.

EW staff will continue alerting district councils, landowners and other agencies, if flood alarms are triggered. Operational staff are available at all times to respond to any scheme maintenance issues that may arise.

 

Weather forecast and warnings

The weather forecast for the Waikato Region is summarised as follows:

Day Weather forecast
Sunday 10/8/08 Fine and crisp. Evening frosts. Not much wind.
Monday 11/08/08 Fine and frosty at first, but cloud increasing from afternoon. Northerlies, becoming strong in exposed places at night.
Tuesday 12/08/08 Rain easing to showers. Strong gusty northerlies turning northwest and easing.
Wednesday 13/08/08 Occasional showers. Gusty westerly winds.
Thursday 14/08/08 Showers. Gusty west or northwest winds.

There are currently no severe weather warnings in force for the Waikato Region.

Observed rainfall

The Waikato Region has received no significant rainfall over the past 24 hours, which is a trend that looks set to continue until this evening.

Response of river systems

Taupo Catchment River systems

Rainfall in the Lake Taupo catchment has eased since last week and consequently the river systems that Environment Waikato monitors have receded to normal winter levels.

The rise in level of Lake Taupo has slowed and is holding steady at RL 357.131 m. This is due to a combination of reduced inflows and also an increased outflow into the Waikato River hydroelectric scheme.

Waipa and Lower Waikato River systems

The flood event caused by the rainfall event last week has passed through the Waipa River and Waikato river systems

The following table provides a summary of observations at key monitoring sites.

River Flow Level Trend Peak level
Waipa at Otorohanga 73 m3/s 30.136 m Falling 33.028 m @ 18:45 3/8/08
Waipa at Pirongia 266 m3/s 18.84 m Falling 22.844 m @ 14:55 4/8/08
Waipa at Whatawhata 385 m3/s 15.619 m Falling 18.824 m @ 10:30 4/8/08
Waikato at Hamilton 441 m3/s 14.165 m Steady 14.965 m @ 14:30 31/7/08
Waikato at Ngaruawahia 774 m3/s 11.58 m Falling 12.734 m @ 08:10 5/8/08
Waikato at Huntly 830 m3/s 9.486 m Falling 10.379 m @ 19:20 5/8/08
Waikato at Rangiriri 881 m3/s 7.645 m Falling 8.374 m @ 16:15 5/8/08
Waikato at Control Structure
(control gate open)
N/A 5.171 m Falling 5.562 m @ 08:15 6/08/08
Waikato at Mercer 1,135 m3/s 4.799 m Falling 5.215 m @ 05:10 6/08/08
Waikato at Tuakau   3.323 m Falling 3.709 m @ 06:00 6/08/08
Lake Waikare
(control gate fully open)
  5.996 m Falling 6.039m @ 18.35 08/08/08
Whangamarino (Gate)   5.188 m Falling 5.59 m @ 3:25 06/08/08
Whangamarino (Ropeway)   5.349 m
5.604 @ 10:25 06/08/08
Whangamarino (Falls Rd)   5.567 m
5.699 @ 15:15 06/08/08

All sites monitored by Environment Waikato on the Waipa River are now receding and having peaked at levels that were below both the 1998 and 2004 flood events. It is however important to note that some ponding adjacent to main river channels may persist for some days yet. It is recommended that landowners continue to monitor the situation closely, particularly given that some rainfall is expected in the next few days.

The flow entering the Waikato River from the Karapiro Dam has remained reasonably consistent over the past week and is now being reduced as the impact of last week’s rainfall diminishes. This situation, combined with the lack of significant rainfall over the past few days, has resulted in the river level at Hamilton being steady. Further downstream, the river is receding, as the peak river flow moves out of the Waipa River and the Lower Waikato River system.

Despite this observed slowdown in rising river levels, it is important to appreciate that river levels will remain elevated in some areas for some days yet, especially within the Whangamarino Wetland and including ponding on land adjacent to the main river channels and drains. It is recommended that landowners continue to monitor the situation closely.

EW will continue to monitor this flood event. This includes working with Mighty River Power to determine the most appropriate operating regime that will support the management of the event.

Coromandel and Kaimai Ranges

In general, river levels in the Coromandel Peninsula have receded from what has been observed over the past week. EW will continue to monitor the various river systems in this area.

Waihou and Piako Rivers

The Waihou and Piako Rivers continue to recede. However ponding on low lying land may persist for some days yet.

EW is continuing to monitor, inspect and respond to any operational issues, such as removal of fallen trees and debris from the main rivers channels. It is recommended that landowners keep a close eye on river and ponding levels, particularly given that some rainfall continues to be forecast for the Waikato Region.

Environment Waikato response

Emergency Management

Environment Waikato emergency management staff are maintaining a flood monitoring and response centre at the main EW office in Hamilton East. Staff are monitoring the situation around the clock, with council officers maintaining contact with operations staff, along with the regional and local civil defence operations. Staff will continue to monitor the situation and respond as necessary.

All Emergency Management issues should be forwarded to the duty Emergency Management Officer on (027) 499 2120 or email emo@ew.govt.nz.

Operations

Environment Waikato operations staff continue to respond to various operational issues in the areas affected. The issues that have arisen thus far mainly relate to ensuring the continued operation of various scheme assets during this flood event (e.g. stopbanks and flood pumps), primarily in the Lower Waikato, Waihou and Piako flood protection schemes. Also, given that river levels are expected to remain high for some time yet, staff are closely monitoring the performance of scheme stopbanks on the Lower Waikato River.

Operational staff from Environment Bay of Plenty are available as additional support and will be assisting EW staff where required. This includes the provision and deployment of mobile flood pumps.

All operational issues should be forwarded to the RCS Operations Manager (Guy Russell).

Technical

Environment Waikato technical staff continue to assist with flood peak forecasting and how this event will progress through the Waikato and Waipa River systems over the coming days. This includes the provision of the forecast information that is contained in this situation report and liaison with Mighty River Power.

Technical staff are also providing support and advice to the flood response team and operations staff in respect to the operation and inspection of the Waihou, Piako and Lower Waikato flood protection schemes.

All technical issues should be forwarded to the RCS Technical Manager (Ghassan Basheer).

Telemetry

The Environment Waikato telemetry system is fully functioning, with support staff remaining on stand-by to respond as necessary (including IQuest and EW IT support).

All afterhours telemetry issues should be forwarded to IQuest support (Michael Cook).

Communications

Environment Waikato communications staff are fielding media enquiries and are producing media releases as required, which are being posted on EW’s website along with the situation reports.

All communications issues (including media enquiries) should be forwarded to the communications duty officer on (021) 369 815.

Waikato Civil Defence and Emergency Management Group

Environment Waikato is continuing to work with the Waikato Civil Defence and Emergency Management Group to monitor and respond to this event. The Waikato Valley EOA and Waikato Group EOC will continue to release situation reports at regular intervals providing an overview of civil defence issues in the Waitomo, Otorohanga, Waipa and Waikato Districts, along with Hamilton City.

All civil defence issues should be forwarded to either the Waikato Valley EOA or the Waikato Group Emergency Operating Centre.

Distribution of situation report

Environment Waikato

Emergency Management Officers
EW Council Chairman
EW Councillors
EW Zone Chairs
EW Chief Executive
EW EMT
RCS Operations
RCS Technical
RCS RHEM
RCS Coromandel Zone
RIG Environmental Monitoring
EW Communications

Other organisations

Waikato GEOC
Duty Waikato Group Controller
Waikato-Valley EOA
Thames-Valley EOA
Southern EOA
Mighty River Power
MCDEM
NCMC
Federated Farmers
Rural Support Trust

Further information

Further information regarding this flood event can be obtained from the following sources:

    • River level and rainfall information: www.ew.govt.nz

 

    • Civil defence information: www.waikatoregioncdemg.govt.nz

 

    • Latest weather information: www.metservice.co.nz

 

    • Road conditions: www.aaroadwatch.co.nz

 

  • Northland Region information: www.nrc.govt.nz

Situation report update

This situation report will be updated by at 09:00 on 11 August 2008 (or earlier if required).

 

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