River Modelling
Clear provides the specialist technical expertise in all of the principal 1-D and 2-D river modelling packages accepted by the Environment Agency including HEC-RAS, ISIS and InfoWorks.
River models are used to predict flows in watercourses, flood extents, flood levels and to investigate the impacts of restrictions such as bridges, culverts and blockages. Hydrological assessments are undertaken using industry standard techniques and software such as the Flood Estimation Handbook (FEH), WinFAP and ReFEH. The reliability and robustness of any model is determined by the accuracy and resolution of the survey data on which it is based. Therefore, the selection of river cross-sections and structures to be surveyed is of paramount importance.
ISIS and ISIS-TuFlow
ISIS Flow is a one dimensional open channel and culverted flow simulation engine which can handle complex structures. ISIS can be linked to TuFlow a 2-dimensional modelling package which can be used to produce an animation of the direction and speed of floodwater across the floodplain or a static image highlighting a certain time-step of interest or the point at which the peak flood level is reached.
InfoWorks RS and InfoWorks 2D
InfoWorks includes a suite of products which aims to embrace the water cycle as a whole from supply and distribution, urban drainage and wastewater management through to river management modelling. The InfoWorks RS module is used to simulate flows in rivers, in channels and on floodplains. The InfoWorks 2D module is used in conjunction with InfoWorks RS to assess the direction and depth of flooding in specific areas and is particularly useful on developed floodplains, urban streets and buildings, road intersections and other transport infrastructure. As with the results from TuFlow modelling, the results from the InfoWorks 2D model can be presented easily and clearly in MapInfo.
HEC-RAS
Created by the US Army Corps of Engineers, HEC-RAS is designed to perform one-dimensional hydraulic calculations for a full network of natural and constructed channels. Models can be run using steady state and unsteady flow conditions.
Survey Requirements
The relevance and usefulness of any model depends very much on the data input into the model. For 1-dimensional modelling a cross sectional survey of the watercourse and the floodplain will be required and must include information on any structures and any significant changes in the watercourse profile, direction and slope.
For 2-dimensional modelling LiDAR data and ideally also a topographical survey will be required to generate the digital terrain model.
