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The Jubilee River story - The Conveyance and Afflux Estimation System
Apart from structural damage and an out-of-court settlement, substandard design and construction of the Jubilee River project between 1996 and 2002 has resulted in a significant maximum conveyance capacity shortfall. This section below is a bit technical, and you will need to know that Afflux (from Google) - is the rise in water level (above normal) on the upstream side of a bridge or obstruction caused when the effective flow area at the obstruction is less than the natural width of the stream immediately upstream of the obstruction.
Extract from http://www.river-conveyance.net/ (The CES/AES software is downloadable from the river-conveyance web site)
The Conveyance and Afflux Estimation System (CES/AES) is a software tool for the improved estimation of flood and drainage water levels in rivers, watercourses and drainage channels. The software development followed recommendations by practitioners and academics in the UK Network on Conveyance in River Flood Plain Systems, following the Autumn 2000 floods, that operating authorities should make better use of recent improved knowledge on conveyance and related flood (or drainage) level estimation. This led to a Targeted Programme of Research aimed at improving conveyance estimation and integration with other research on afflux at bridges and structures at high flows. The CES/AES software tool aims to improve and assist with the estimation of:
In 2001, a Scoping Study by the UK Network on Conveyance in River Flood Plain Systems confirmed the potential for reducing the uncertainty associated with estimating flood levels. The main drivers were the advances in the understanding of flow phenomena in complex river and coastal flood systems; the availability of over twenty years of data from the EPSRC Flood Channel Facility at HR Wallingford; the advent of computing power that enables more sophisticated solution techniques; and concern that this new knowledge was not well transferred into practice within the UK flood management community. This led to a Targeted Programme of research to develop a new Conveyance Estimation System.
The final product is a software tool for estimating conveyance (water levels, rating curves, etc), spatial velocities and boundary shear stresses at river sections as well as undertaking simple reach-based backwater calculations. It also provides a comprehensive database of river roughness, integrating diverse information from over 700 references, including photographs (linked to the River Habitat Survey) and advice on vegetation cutting and regrowth.
In 2003, a Scoping study into the 'Hydraulic performance of bridges and other structures, including effects of blockage, at high flows' confirmed the potential for drawing together much improved guidance for practitioners on the estimation of afflux at in-channel structures. In 2004, a second complementary project was commissioned to develop the Afflux Estimation System (to operate with the CES) and the Afflux Advisor (an Excel spreadsheet application).
The aim of the project was to improve the understanding of the effects of in-channel structures on flood water levels at high flows, relating particularly to the representation of afflux (the increase in upstream water levels attributable to the structure). The project researched a range of methods of calculating afflux, to determine their applicability to the various types of bridges and culverts found in UK channels and incorporated the most appropriate methods and algorithms, following detailed testing, into the AES software.
For further information please visit http://www.river-conveyance.net/