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Innovation & Research


Issue No. 91 IN thIs Issue


Alternative Energy Alternative future energy pathways 2


Buildings Building envelope impact performance 8 CO2


Emissions Alternative future energy pathways 2


Construction Process Light-steel framing/modular construction


3


Decision-making Multi-objective optimisation in FRM 4


Flood Risk Management Multi-objective Optimisation in FRM 4


Materials Building envelope impact performance 8 FRP strengthening


Light-steel framing/modular construction


7 3


Meteorology Infrastructure for hydro-meteorology 6


Modelling Infrastructure for hydro-meteorology 6


Policy Alternative future energy pathways 2


Structural Repair FRP strengthening


7


Sustainability Future Cities – opportunity for growth 5


Testing Building envelope impact performance 8


A


research project by HR Wallingford is updating its Reservoir Survey


Analysis and Sedimentation Simulation (RESSASS), a one- dimensional numerical model used to simulate long-term de- position patterns in reser- voirs. The new model can now be applied to most types of river-reservoir systems, and includes capabilities such as limiting the outflow capacity of the reservoir and distribut- ing the outflow between differ- ent outlets. The model is able to consider dif-


ferent sediment size ranges. The transporting capacities for the sand and larger sizes (greater than 0.063 mm) are calculated separately from finer sediments, silts and clays that are in the cohesive size range. The transport rate of sediment, particu- larly that of fine fractions, does not adapt instantaneously to the changes in transport capacity. Part of the research has focused


also at www.innovationandresearchfocus.org.uk November 2012 Modelling reservoir sedimentation


Every year, sedimentation causes an estimated one per cent reduction in the total capacity of all reservoirs worldwide. Sediments also block intakes in reservoirs and damage tunnels and turbines. The use of numerical models for simulation of reservoir sedimentation enables the key parameters of reservoir life to be predicted over the long term. In particular they can provide information on the distribution of sediment within a reservoir; a key issue for the project’s lifetime and the planning of manage- ment measures.


(Top) Sediment deposits of sand material in the upper catchment of the Indus River.


on incorporating decay functions to model the non-equilibrium condi- tions when transport capacity decreases in the flow direction and in the case of increasing transport capacity, developing erosion thresh- olds. The interaction between the different sedi- ment sizes and their impacts on transport capacity are also considered. The density and level of compaction of deposited sediments is also taken into account to estimate volumes of material deposited or eroded. Flushing consists of remobilising and


transporting deposited sediments through the reservoir using low-level outlets. This is done by increasing flow velocities and drawing down the reservoir water level. The new version of RESSASS includes a simplified approach to simulate flushing operations in wider reservoirs that takes into account


www.innovationandresearchfocus.org.uk


(Above) Advance of the delta in a reservoir calculated with RESSASS.


existing knowledge on real flushing channels. This research has advanced the develop-


ment of methods and tools to predict reservoir sedimentation and the impacts of sediment management options. Replacement of storage by constructing new dams is expensive, can be environmentally and socially damaging, and is often politically unacceptable. This new im- proved tool is aimed at supporting asset man- agers in developing future operating policies for reservoirs that are more-sustainable.


For further information contact Dr Marta Roca Collell, Principal Engineer, HR Wallingford Floods Group (01491 822303; E-mail: m.roca.collell@ hrwallingford.com).


Innovation & Research Focus Issue 91 November 2012 1


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