Articles & Case Studies

Designing For Climate Change - Micro Drainage software automates new planning compliance for civil engineers

Posted: Friday 20th April 2007

New developments in civil engineering design software are confronting the reality of climate change in the UK. WinDes®, the industry-standard drainage design suite from Micro Drainage of Newbury, features new modules and additional functions that are designed specifically to address the latest regulations governing planning and development, in the light of rapidly changing weather patterns.

Serious flooding in the UK used to be a comparatively rare event; these days, every year brings a major problem. Boscastle, Carlisle, York - these names and others have become synonymous with deluged houses, impassable streets and rocketing insurance premiums.

The response of the Department for Communities and Local Government (CLG) has been to produce Planning Policy Statement 25, better known as PPS25, on the subject of Development and Flood Risk. This document sets out the recommended approach for planners, local authorities and developers seeking to build new developments, or to extend existing sites - the approach being risk based.

For civil engineers, the challenge is to keep pace not only with the rate of change in the weather, but also with the regulations that are trying to accommodate it. With the latest additions to the WinDes®suite, Micro Drainage has pioneered a range of CAD-based techniques that have automated many of the demanding procedures now required of civil engineers.

One of the most crucial of these developments is the ability to prepare flood risk assessments in line with the requirements of PPS25. For developers, the issue is critical; if a proposed development does not comply with the flood risk criteria, it cannot be insured - which means it cannot be mortgaged and cannot be sold.

The guidance includes a Sequential Test, designed to match the vulnerability of the development to the level of risk, and an Exception Test, to be applied where there is apparently no suitable alternative site. The core modules within WinDes® all combine to provide help in preparing flood risk assessments (FRAs).

Climate change has also been built-in to the core functions of the software. The Seasonal Return Period Wizard, which automates the testing for all storm durations, and the Design Audit Wizard, which provides rapid auditing of a given design against multiple failure criteria, both incorporate the ability to account for climate change in their calculations.

An assessment of a new development may now be audited in accordance with the requirements of the Interim Code of Practice for Sustainable Drainage Systems. This process checks the discharge rate of a new development for the 1, 30 and 100 year return periods, against the greenfield or pre-development runoff. It also looks at the the pre and post-development runoff volume balance for the 100 year, 360 minute storm duration, and applies the minimal discharge test, for the 5mm rainfall depth.

Aidan Millerick, managing director of Micro Drainage, points out that there are two important aspects to the question of compliance:

“These regulations are there to deal with genuine threats,” he says. “Compliance is important because it can significantly reduce the danger of flooding and the distress that it causes.

“However, the other key benefit of this software for engineers is the ability to demonstrate the compliance of their designs. What we are talking about here is planning consent - an extremely sensitive and competitive area - and designs that cannot withstand the scrutiny not only of the planning authorities, but also of the Environment Agency, are doomed to fail.”

Another new addition to the WinDes® suite is the FloodFlow module, currently offered on a free-trial basis. It extends a function already built-in to the Advanced Productivity Tools (APT), which is the ability to model flood flow paths.

This is a requirement of Sewers For Adoption 6 (SFA6), the regulation governing the suitability of drainage systems for adoption by water companies. SFA6 also takes account of PPS25, and the Interim Code of Practice (ICP) for Sustainable Urban Drainage Systems (SUDS).

Using the flow path modelling capabilities within APT, and the new FloodFlow module, engineers can create designs that demonstrate where the most sensitive areas may be, and the solutions that will mitigate the risk. FloodFlow provides overland 2D analysis to graphically demonstrate the direction, depth and velocity of overland flows, addressing the risk and exceedance issues that will be scrutinised by the approving authorities.

To help engineers keep pace with the latest legislation, and the range of new functions in the industry-standard drainage design suite, Micro Drainage continuously updates the five WinDes® training courses. Half-day workshops are also run regularly, and both the training and the workshops can contribute to Continuous Professional Development programmes (CPD).

Says Aidan Millerick: “We are operating in the most demanding regulatory climate engineers have ever known. But we’re also working with the most demanding climate patterns that engineers in the post-industrialised era have ever known.

“Compliance is critical if we are to avoid the flooding that can lead to years of misery for the people whose lives it affects. The CAD techniques within WinDes® can help engineers create compliant, effective designs, while saving time and money through the use of advanced automation.

For Further Information

For further information about WinDes® and Micro Drainage, including details of training courses and free workshops, visit, call 01635 582555, or email

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