6/28 Langston Place
Epping NSW 2121

PO Box 352
Epping NSW 1710

T : 02 9868 1966
F : 02 9868 5759

Example of flood risk mapping

Flood Risk Assessment

Computer Simulation of Flood Behaviour
Since its establishment in 1986, Bewshers have specialised in the assessment of flooding and stormwater inundation in both urban and rural areas. This has ranged from site-specific locations to whole catchment assessments for both the private and public sector. Over twenty of these studies have been completed with government funding under the NSW Floodplain Development Manual and its predecessors.

The firm has extensive experience in using a wide range of hydrologic and hydraulic models and uses that experience to choose the most appropriate modelling platform for each study.  This includes the use of the latest two-dimensional (2D) modelling software (which is the Australian-written TUFLOW package) to assess a variety of often complex flood regimes which previously were only able to be crudely modelled using either one-dimensional (1D) or quasi-2D modelling packages.  Some of the most significant advantages of the TUFLOW software are its abilities to interactively model both underground stormwater networks and surface flooding, to model complicated flow behaviour along streets and between buildings, to produce high quality flood maps and to provide computer animations of flood behaviour.  In particular, maps of flood extents, flood level contours, velocity distributions, and flood risk precincts can be readily prepared through its built-in interface with commercial GIS packages. 

It is important that wherever possible, flood models should be calibrated using historic flood information.   Often this requires catchment-wide community consultation and Bewshers have developed specifically tailored questionnaires to gather historic flood data from residents and business owners for many of our flood study commissions.  As part of major studies, the firm has advocated and undertaken public displays of the behaviour of important historical flood events that have been simulated in the flood models.  This publically validates the models and allows local communities to gain a first hand understanding of their flood problems.

Development Advice
Bewshers have over 25 years of experience in providing best practice advice for floodplain developments.   This advice and the associated services have been provided for more than 500 urban and rural projects involving flooding and stormwater inundation issues.

The skills which our firm brings to these projects include:

  • computer modelling of flood behaviour;
  • identification and communication of current best practice floodplain management;
  • assessment of third party flood impacts;
  • formulation of appropriate policies and controls to manage floodplain developments;
  • assessment of flood risks to people and property;
  • urban drainage investigation and design;
  • environmental assessment;
  • on-site stormwater detention assessment;
  • design and documentation of flood mitigation works; and
  • the provision of independent and expert testimony in many dozens of court proceedings relating to flooding and stormwater inundation issues.

Bewshers' directors are committed to a 'hands-on' approach and have direct involvement in each project, taking responsibility for co-ordination and completion of the firm's commissions.  This has given our firm an excellent track record in providing high quality advice on development projects in an efficient and cost-effective manner.

Design and Documentation of Water Related Projects
The firm specialises in the design and documentation of flood mitigation structures and the drainage components of urban developments and major infrastructure projects.  The firm’s expertise includes feasibility studies, detailed design and preparation of contract documentation for projects such as:

  • stormwater detention basins;
  • major trunk drainage systems including refurbishment and enlargements;
  • creek restoration projects;
  • on-site stormwater detention (OSD);
  • road drainage systems;
  • bulk earthworks and land grading relating to catchment management;
  • cross drainage design for major road and rail infrastructure projects;
  • specialist stormwater pit design and streamlining;
  • stormwater components of urban developments; and
  • golf course and sports field drainage and water supply schemes.