Arrangements for Flood Warning Services in Victoria
February 2001



4. Flood Warning System Responsibilities

Responsibilities and cost sharing for flood warning are founded on the previous service principles but also based on considerations for addressing all parts of the flood warning system. These considerations and associated responsibilities are listed in Section 4 and reflected in Sections 5, 6 and 7 which highlight the responsibilities of agencies from Commonwealth, State and Local Government, regional authorities, and also the community. Appendix 5 contains an in-depth listing of considerations and associated responsibilities for data collection networks (Section 4.3).

For flood warning services to develop and continue to be effective, there must be cooperation between all stakeholders. Within this cooperation and in addition to responsibilities it is essential that the cost sharing principle of 'beneficiary pays' applies to the management and maintenance of the flood warning system.

The nature of these responsibilities and cost sharing principles may differ depending on when a flood warning system upgrade occurred. Upgrades are undertaken when there is a clear agreement between the key parties that there is a need for an upgrade and a commitment to adhere to the following responsibilities and cost sharing.

Buckley Falls, Geelong, November 1995. Photograph, 'Geelong Advertiser'

4.1 Funding Principles

Commonwealth and State Government support the provision of flood warning services by meeting the capital costs of new and upgraded flood warning systems through available agency budgets and funding programs such as the Regional Flood Mitigation Programme and on the recommendation of the VFWCC.

Local Government, in general, provide little or no initial capital funding because they provide substantial in-kind contribution to capital works and are responsible for the annual maintenance costs of many parts of the system. These costs can cover the data collection network, the community alerting system, and flood warning dissemination. Also, Local Government would normally be expected to cover the replacement costs of equipment at the end of its useful life.

Local Government may contribute to capital costs where there is a specific local requirement that would be outside Commonwealth and State Government contributions or where funding programs do not provide sufficient funds.

Catchment Management Authorities may contribute to capital and ongoing costs where there is relevance to their activities. Water Authorities on the other hand clearly contribute to capital and ongoing costs where there is relevance to their activities. For the Greater Melbourne area, Melbourne Water covers the costs of its flood warning services through part of its Drainage and River Improvement Rate paid by the owners of rateable properties.

It should be noted that in addition to funding contributions there is usually substantial in-kind contributions with upgrading the warning system from the Bureau of Meteorology, Local Government, Catchment Management Authorities, Water Authorities, Victoria State Emergency Service and Department of Natural Resources and Environment.

4.2 System Review

The VFWCC reviews flood warning system performance and is generally responsible for initiating system reviews around the State. Some reviews are initiated at local, regional or agency level. Typically each organisation involved in flood warning (especially Local Government) would attempt some level of review. System reviews need to be undertaken periodically and specifically after a significant flood event in order to capture system performance characteristics and follow through with improvements.

4.3 Management of Data Collection Networks

Data collection networks for flood warning consist of:

  • The formal network of raingauges, stream level gauges, flow measurement equipment, telecommunications, data storage and display facilities;
  • The informal local network of people who record and relay information on what is happening in parts of the catchment.

Both these components are essential for flood prediction and the dissemination of flood information. To ensure the integrity of information it is essential that the roles and responsibilities for the management and maintenance of the existing and future data collection networks be clearly established.

The formal data collection network of gauges and associated equipment around the State have evolved over many years and have varying degrees of sophistication. They are operated under a variety of management setups, which typically reflect their evolution as a cooperative effort between interested parties. The roles, responsibilities and cost sharing associated with these networks are detailed in Appendix 5 and summarised in Table 1 of Appendix 5. These roles and responsibilities are broadly reflected through sections in the ARRANGEMENTS dealing with principles, warning system considerations and responsibilities.

The informal local network of people relay information through procedures set out in the flood sub plan of the respective Council's Municipal Emergency Management Plan. Sometimes this information includes rainfall and stream level information. The management of these people and information flow is the responsibility of Local Government. Water authorities, CMAs and other agencies may provide assistance.

4.4 Emergency Callouts for Network Maintenance

In order to ensure the effective operation of flood warning systems, it is necessary to ensure that any equipment malfunctions in the rainfall and streamflow data collection networks are rectified as speedily as possible, particularly during flood events.

Prior to monitoring partnerships (Appendix 5) being established in a region, owners of rainfall and hydrographic stations will fund and provide emergency callout services for essential repairs to equipment (including telemetry equipment) at rainfall and streamflow stations where these are necessary for the operation of the flood warning system.

Once monitoring partnerships are established in a region, the Partnership Manager is responsible for funding and providing this emergency callout service.

The station owner/Partnership Manager and agency responsible for flood prediction are to resolve details of the callout services required. Authorisation of repairs is at the discretion of the agency responsible for flood prediction.

Repairs are to be carried out with the following emphasis:
  • Highest priority is to be given to the efficient operation of emergency services and the protection of life and property.
  • Second highest priority is to be given to the flood monitoring responsibility.
4.5 Rating Tables

Information of stream levels and, in some cases, flows are required for flood prediction purposes. Where flow information is required, rating tables which define the relationship between water level and flow in a stream must be derived. These tables are derived empirically by gauging across the full range of flows (including flood flows).

Owners of data collection gauging stations are to provide available rating tables for sites that require such tables to agencies involved in flood prediction (at no cost to those agencies). In situations where station owners do not require ratings over the full flow range, but flood prediction agencies require the full flow range, then contributions to the cost of rating high flows may be negotiated from beneficiaries.

4.6 Flood Prediction

Flood prediction is about estimating the height of water at a specific place at some future specified time. The place is usually a gauging station which is often located in or near a town. The prediction may be expressed in many ways. For example, it may be as:

  • A value ­ e.g. 7.5 m
  • A range ­ e.g. between 7.5 and 7.8 m
  • Being above a particular value ­ e.g. greater than 7.5 m
  • A class of flooding ­ e.g. minor, moderate or major

Predictions are made by combining weather forecasts, observed rainfalls, stream levels, knowledge of catchment conditions and operations of water storages through predictive techniques. Commonly used techniques are:

  • stream height and flow correlations which only provide an estimate of the peak height or flow
  • rainfall runoff models which allow prediction of the hydrograph at the forecast location.

Organisations with a responsibility for flood prediction must meet the costs of flood prediction in addition to any data collection network responsibilities. Flood prediction responsibilities include capital costs and operation and maintenance of computer hardware and software, flood prediction techniques and support to software users.

There are a number of considerations with flood predictions. Key ones are:

  • Flood prediction may be performed by one or more key organisations, or at local level. However, there must be no competition between groups doing predictions. There must be one prediction or set of predictions issued (as part of a flood warning) by the responsible group which is consistently relayed to those in need.
  • Agencies and communities need to appreciate that it is not possible to be exact about a prediction. There are still many uncertainties in weather prediction and understanding of catchment behaviour. The availability of rainfall stream level (& flow) data is critical to the prediction. Sometimes data is not available and only broad indications of flooding may be provided.
  • The predictions must be in a format that can be easily interpreted by response agencies and the community.
  • The vertical extent of flooding can be effectively translated into horizontal extent through use of flood inundation maps and/or guides which show the effects at respective gauge heights on property and infrastructure.


Figure 3. Example hydrograph showing the rise and fall of stream level over time commonly observed at a stream gauge. The dotted section shows the output from a flood prediction model.

Figure 3. Example hydrograph showing the rise and fall of stream level over time commonly observed at a stream gauge. The dotted section shows the output from a flood prediction model.



4.7 Flood Sub Plan of the Municipal Emergency Management Plan (MEMP)

The MEMP is prepared and implemented by municipal councils under the Emergency Management Act 1986. The MEMP incorporates a risk management approach and is a key to local emergency planning and contains sub-plans for many types of local emergencies one of which is flooding.

As part of the MEMP, municipal councils with high flood risk areas need to prepare a flood sub plan which includes strategies for flood management. This includes methods of alerting their community, dissemination of flood warnings and information, monitoring and recording of flood information, as well as other items. Flood sub plans can be for a regional area or for an urban centre. Any development or upgrade of flood warning systems must be reflected in these flood sub plans. VICSES is responsible for assisting Councils in the preparation of their MEMPs and respective sub plans and for the auditing Council's MEMP and respective sub plans.

4.8 Dissemination of Flood Warnings & Related Information

The responsibility for disseminating warnings and related information to the communities at risk at the onset or during periods of flooding rests in the main with the Bureau of Meteorology, VICSES and Local Government. The dissemination is in accordance with agency responsibilities and specific local arrangements in the respective Flood Sub Plan of the MEMP.

Melbourne Water and other water authorities have an associated responsibility to provide support and advice for dissemination in relation to their systems operation before and during periods of flooding. This is especially the case with dam and weir operation.

4.9 Community Alerting & Local Action

A critical part of any flood warning system is the prompt alerting of the community that flooding will occur. This alerting must be able to operate at any time and is usually through a variety of means.

The prime responsibility for implementing and operating flood alerting procedures for communities rests with Local Government, VICSES and Police. Local Government has responsibility for actions at local level in order to respond to the flood. The alerting procedures and actions are contained in the Flood Sub Plan of the MEMP. In the Greater Melbourne area Melbourne Water may be able to provide assistance to Local Government.

4.10 Community Education

Community education about flooding is vital for people in and surrounding flood affected areas. This education is paramount to the community's effective response. Responsibility for education is primarily a Local Government, VICSES and Catchment Management Authority responsibility. The VFWCC (particularly the Bureau) provides assistance where required. Information which is produced in flood warning system upgrades (e.g. response guidelines, flood level information guides, flood inundation maps etc.) should be used to improve community awareness.

4.11 Flood Category Levels

At key flood prediction locations, flood category (or class) levels are set for heights or flows at predetermined levels in order to classify the flooding as either minor, moderate or major (Appendix 4). The level or flow is set such that the flood effects above this height reflect the category of flooding. Flood category levels are not based on flood frequency, they are based on the likely flood impact for a particular locality. Heights are set in metres to a local datum or to Australian Height Datum. Flows are in megalitres per day or cubic metres per second.

The responsibility for setting flood category levels rests with Local Government with guidance from the VFWCC to ensure statewide consistency. As members of the VFWCC the Bureau of Meteorology and Catchment Management Authority provide the main guidance along with Melbourne Water for Greater Melbourne. Levels are not static and may change as more flood impact information becomes known.

The Bureau of Meteorology keeps a record of flood category levels and flows. For Greater Melbourne, Melbourne Water keeps a similar record of flood category levels and flows.

FLOOD INFORMATION GUIDE
GAUGE NAME:Tallandoon   RIVER:Mitta Mitta
Key Heights (metres) 1. Minor: 4.2 2. Moderate 4.9 3. Major: 5.6
Height
(m)
Flow
(ML/day) Date
Effect Location Action
5.97 93,000 Aug 1955
5.66 62,500 July 1974 Bridge on Omeo Highway inundated. Some rural houses isolated and some flooded above floor level. Two kilometres downstream of the junction of Lockharts Gap Road and Omeo Highway
  • Rural evacuations required downstream of this location.
5.6 60,000 Major Flood Level
5.55 52,400 Nov 1974 Omeo Hwy inundated for 8 km From Tallandoon downstream
  • Liaise with VicRoads re road closure
  • Evacuation only possible upstream via Omeo
5.48 47,300 Sept 1975
5.37 39,700 Oct 1974 Omeo Hwy cut at 40,000 ML/day Upstream and downstream of Tallandoon
  • Lockharts Gap Road not accessible
5.12 30,700 Nov 1996 Water over road at Tallandoon
(Highest flood event since Dartmouth Dam construction)
  • Liaise with VicRoads re notification of road closure
  • Limited vehicle access ­ 4WD only
4.9 25,700 Dec 1992
Second event
Moderate Flood Level
Widespread inundation of farmland
Below Tallandoon
  • Further stock movement to higher ground required
  • Consider future closure of Omeo Highway at 40,000 ML/day and impacts on evacuation routes
  • Consider property evacuations
4.3 17,800 Nov 1992
4.2 16,500 Dec 1992
First event
Minor Flood Level Pigs Point camping area inundated
  • Consider stock movement
  • Campers evacuated
3.7 12,655 Sept 1983 Inconvenience to landholders Low lying grazing land inundated
  • Possible stock movement required in the lower reaches of the river
  • Additional information required to know what/where inconvenience occurs
3.4 10,000 Irrigation pumps affected Tallandoon (bank full) Downstream of Tallandoon
  • Community/farmers to monitor flows for impact on pumps
  • Landholders to contact Dartmouth Dam telephone flow advice
NOTE: This guide is to be used in conjunction with official flood warnings and local procedures by Towong Shire's Emergency Management Group.

Example Flood Inundation Guide



4.12 Monitoring and Recording of Flood Information

Monitoring of rainfall and stream level data is an ongoing activity through the year. In flood times the monitoring and recording activities are much greater than in non flood times. The availability of high quality up to date flood data is essential for informed decision making.

The collection of real time flood data during and immediately after an actual flood event offers the best opportunity to review and enhance existing flood data and flood warning systems. The Victoria Flood Management Strategy lists the types of information that needs to be collected. Building on this list for flood warning and overall flood management, items to be monitored and recorded include:

  • peak flood flows and levels. Levels to be surveyed where possible;
  • aerial flood photography and ground based photographs of flood impacts and extents;
  • flood damages to buildings, crops, infrastructure, stream bed and banks etc;
  • records of, and any problems with, the effectiveness of communication systems and warning dissemination processes;
  • effectiveness of existing flood management measures (e.g. mitigation works, flood warning and response measures);
  • operation of reservoirs.
  • loss of access and evacuations.

In order to update flood data, learn from actual flood events and improve the warning system, agencies which have flood management and/or flood monitoring responsibilities should record the above information. This includes Local Government, Catchment Management Authorities, Water Authorities and VICSES.

Wherever possible recording efficiencies are to be applied between organisations. Permanent archives of the above information are to be kept by the agencies with a flood monitoring and recording responsibility. Refer to the Victoria Flood Management Strategy for any additional clarification outside of these ARRANGEMENTS.

4.13 Archiving of Data and Station History

Owners of data collection networks are to provide permanent archiving of rainfall, staff gauge height, equivalent streamflow where a rating is required, and gauging station history. The Department of Natural Resources and Environment provides archive assistance through storing this data and associated information in the State Data Warehouse.



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