Floods, drought, climate

Extremes in nature can have significant influence on business operations. Whether needed for planning, operations or closure activities, or even for risk management and insurance requirements, Fourth Element understands the variability of events in nature and can convert the uncertainty to meaningful risk values that support business planning. Furthermore, we assist in identifying solutions to avoid, mitigate or manage this risk. We have over 20 years experience in flood management and the design of flood relief solutions. Our modelling capability allows the client to explore different scenarios and solutions. We work with specialists in climate modelling and then we translate the scenarios to risks in, for example, water security, food security and disaster risk.

We support environmental impact studies, master planning exercises, etc., providing water resources and hydrological input. These include flood line determination, urban drainage design and flood alleviation studies, catchment and reservoir yield analysis, storm water management, surface water impact assessments, environmental flow requirements and flood management master planning.

Flood line determination

The National Water Act requires that site layout plans need to depict the 100 year flood lines in a form acceptable to the local authority concerned. The local authority may have additional requirements (e.g the 50 year flood line), but they may not be best placed to advise on the accuracy needed. With the growth in readily available software, there are a wide range of flood line services being offered in the market and the Client may not always get what he thinks he asked for.

Flood lines are a measure of risk and are intended to assist in good decision making in planning, design and management, and not all of them require the same level of investigation. Fourth Element has developed two main forms of flood line services; certified flood lines and indicative flood lines. Certified flood lines are detailed analyses specific to each site. They are usually necessary for site design and flood management purposes, as well as most insurance purposes. They require detailed topographic survey, hydrological and hydraulic analyses, and probability assessment. They should be signed off by a certified engineer experienced in river and drainage hydraulics.

Indicative flood lines are a more rapid assessment and often require less topographic and site detail. They are still indicators of flood risk, but are less accurate, often relying on regional or empirical parameters. They are best suited to high level planning and management purposes, and are not normally suitable for site design purposes. They may be acceptable for certain insurance cover, but the client should should disclose this to the insurance company. They still require hydrological and hydraulic analysis, but the analysis is less intensive. Accuracy of indicative flood lines is very often dependent on the experience of the engineer and the data available.

Please send any queries to Fourth Element and we will be happy to help advise you on the specifications appropriate to your requirements.