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Highlighting hydrology

From CAD User AEC Magazine Vol 22 No 3 - FEBRUARY/MARCH 2009

For our second feature on Autodesk's civil engineering software, David York of Autodesk looks at how the EU Floods Directive is bringing hydrology to the attention of planners and developers in Ireland

For an island that perversely prides itself on its rain, Ireland has recently discovered that both water supply and flooding have become urgent issues for many of its urban areas. Some flood threats, like Clonmel, are traditional problems with an all too long history. Other instances would appear to be the fruits of overdevelopment and imprudent planning.

In theory, at least, most of the manmade problems of flooding will not be repeated because of the EU 'Floods' Directive of 2007 and the relevant draft guidelines for the planning process introduced as a result of the inter- Departmental Flood Policy Review Group which reported in 2004. Some significant flood mapping studies have already been undertaken (see www.floodmaps.ie) and a national programme from this year should see the picture for the whole country completed by the 2013 deadline of the Floods Directive. In the meantime, the draft guidelines are already having an impact on the planning system because flood risk assessment is now an integral part of the process. Applications have to be supported by site-specific flood risk assessments, which mean that from the earliest preplanning stage of a development any such risks have to be investigated and assessed. Where there is some risk of flooding, the planning submission must include detailed measures to prevent or alleviate it. The general principle is that a site's characteristics should be no worse after development in terms of flooding, water retention or run-off. One of the practical effects of this tighter regime to avoid or minimise flood risk and storm water damage is that hydrology is a word and a subject that is rapidly becoming more familiar to everyone involved in development, from the one-off house client through developers and construction firms and all of the engineering, architectural and planning professions.

The key to dealing effectively with all of the issues involved is to be found in smart modern software. At a national and regional level, flooding studies are based on GIS (Geographical Information Systems) and companion software for topographical modelling and mapping. On the development side, civil engineering and architectural software offers the necessary tools for the professionals.

"There is a rising level of legislation to ensure better flood and storm water management across Europe, both at EU and at national level," says Ian McGregor, EMIA AutoCAD Civil 3D product manager of Autodesk. "The EU Floods Directive is central, of course, but a long history of neglect and poor management means there have been adverse impacts across a range of related issues including erosion and pollution. By no means all of the adverse affects came from building and infrastructure development. But these are the areas where a difference can be made immediately in every new project planned and in remedial works. What professional software contributes is the ability to calculate and design the optimum solutions, taking in available external data from GIS and other modelling systems."

A major advance is that today's software such as AutoCAD's civil engineering package is natively in 3D. "As well as its sheer power, this represents in many respects a democratisation of planning and development because the visualisation and dynamic modelling that is part of AutoCAD Civil 3D enables all of the parties involved to grasp the challenges of a particular site, or the implications of a proposed design solution." In relation to flood risk, storm water runoff, percolation and so on, the effects of any design modification can be quickly and easily calculated and presented visually.

Working in 3D with a comprehensive civil engineering package is also a more holistic process, Ian McGregor points out. "Traditionally, for example, drainage design was separate from the structural and architectural elements of a development. So the process was staggered between professionals, slow and potentially error-prone. Today with AutoCAD Civil 3D and its specialist Hydraflow extension, all of the elements can be modelled as part of the design stage. Project leaders can examine the 'constructability' of the design, for example, and accurately forecast the cost implications."

Autodesk currently offers 25 country kits for AutoCAD Civil 3D, which enables it to integrate specific local standards. It also works fluently with other regularly used professional software such as Microdrainage WinDes and FloodFlow, while AutoCAD Map 3D is included in the suite and inter-operates with other GIS suites such as MapInfo and ArcGIS. In Ireland the importance of examining site hydrology before entering the planning process is beginning to be widely understood, according to Mark Green, managing director of Galwaybased Amicus Technology which specialises in the provision of engineering and GIS software solutions. "The principal concerns are how to reduce the time the process takes and how to produce figures as accurately as possible for the planning authorities. At the very earliest stages now it is essential to tackle the questions of flood risk and the possible implications for costs and the design solution." Since there will be national flood risk maps and GIS information available and a growing body of similar regional data from the local authorities, it is essential that the engineering software can take in and incorporate the official spatial data. "Between such official surveys, site surveys and surface modelling it is now relatively straightforward to work through the 'what if?' scenarios to assess flood and storm water risk and devise an effective civil engineering solution."

Mark Green feels that accepted conventions will arise fairly speedily in each planning area and in respect of various development locations. "An elevated site, for example, may not require more than clear provision for water run-off while low-lying land will bring in the need for complete flood risk assessment. Given the new national planning policy, which is generally against development on known flood plains, the assessment and the engineering solution may well be basic to securing any permission." Even in built-up areas, infill development or restoration projects will have to meet more rigorous risk assessment and mitigation standards, he says.

City and Council development plans will need to be revised in the light of the new Draft Guidelines (which are expected to be formally adopted after the current consultation period) as well as the Local Area Plans which are based on them. Since the publication of the Draft Guidelines, all planning authorities have, in any event, been mandated to assess all planning applications in accordance with them. So for planners and politicians, engineers and architects and their clients, a strict new regime is coming into being which will, it is hoped, minimise flood risk and damage for the future: and Hydrology is a term that will soon be in everyone's vocabulary. www.autodesk.com

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