Simulation modelling of sewerage and urban drainage systems

How can simulation modelling of urban drainage help to improve development of the town, better drain roads during heavy storms and improve the life of the town?

Plans of development of system of urban rain and sewage water, so called Master Plans, belong to basic documents that secure good development of the whole town. Master plans deal with different systems: combine sewers operated by local waterworks, rain sewers often owned and managed by the town and system of recipient either as open channels or in pipes. Master plan of urban drainage propose the way to solve problems with current state of the drainage system and the help to figure out, where are current problems of drainage system. Master plan is also concerned about the future development of the drainage system of the town as the town will grow. Thanks to it we can see if the current drainage system is sufficient to drain the water or if it is necessary to increase its capacity as the town will grow or change. The plan then enables to improve, step by step, current drainage system according to the priorities of future development of the town. At the same time, Master plan can help to save money as the investment into the drainage system is properly designed. At the same time it enables to eliminate current problems with the urban drainage, or at least to set anticipated amount of finance to improve current and future function of the drainage system. Aquion belongs to the world top in simulation modelling of water supply, urban drainage systems and open channels.

Effluent from the combined sewer system during design rain (n=0,5, t=15 min): current state before and after realisation of proposed measures. (Red dot- outflow to surface, orange line-pressurised flow in pipes)

Problems with urban drainage are quite common. Problems can increase with the occurence of more intensive rains in connection with climate change. Problems can also occur with the growth of town. It means that developed areas covered by impervious surface should be in any way drained.. If the drainage system is developed without a plan, or if the problem is unknown it can happen that with the development of newly built-up town parts or with increase of percentage of impermeable areas within current districts, new problems with the urban drainage system can occur or the current can be more serious. Problems are caused by the incompressibility of the water and by the fact that head loss increases by square of velocity. It means that as the drained area increases, it is necessary to reconstruct pipes and open channels towards higher flow capacity, to build detention storage reservoirs or eventually to search for a new way to lead water out. Without a plan under a time pressure to solve the problem, the selected measure may not be right from the point of view of urban development, technically or financially. This can lead to disaffection of citizens with the administration of town. Aquion can help you to elaborate a conception of improvement and development of urban drainage within the whole town or in the particular watersheds, where the problems occur.

Costs of urban drainage master plan elaboration or costs of design of measures for particular drained areas are not low. On the other hand the money put into this „invisible“ infrastructure should be considered as investment. Proposed solutions are verified using the simulation modelling. That means that very often the final investments can be lower, the preparation of realisation of investments run faster and the administration of the town can have good arguments to explain the necessary development of urban drainage.

Left: Level of water close to surface within a 5-year and 15 minutes rain.    

Right: Course of water table in main sewer after new areas will be drained. 20-years, 15 minutes design rain. 

Somebody can argue that special hydrodynamic calculation is not necessary because local people know where the problems are. We agree with that the local people knows were the problems are , but only computations can show the real causes or where the problems will occur in the future in accordance with the city development. Computations can also help to identify yet unknown problems.

Simulation modelling helps to propose measures that conform with the policy of the town development and its financial sources. Thanks to the simulations the proposals of development of the drainage system cannot be underestimated or overestimated. The proposed measures are the right ones. Only the calculation will demonstrate how the particular element of drainage system behaves during different design or real rains. Are specialists necessary to solve this problems? Are not the local consultants skilled enough? They will probably manage it, but they do not have proper mastership, knowledge and right distance. Aquion saved money of Turnov city (at local parts Daliměřice and Hrubý a Malý Rohozec) in CR when the master plan was elaborated. Turnov saved about 4.3 mil EUR by cancelling of the 1.2 km long tunnel construction to drain rainwater under the buildings.

Important question is if it is possible to plan, design and build more important elements of urban drainage system without verifying the proposed technical parameters using simulation modelling. Sure, it is possible. But proposed solution does not have to work properly and can be much more expensive. Costs to verify proposed investment´s measures are, compared to the amount of money for the investment, quite low. With verification of the proposed measures using simulation modelling you will be sure that selected measure is properly sized and finances will be well invested. Co-operation with Aquion means more safety, confidence and properly invested money into the development of drainage systems. It also means smooth development of town and its life.

Left: Master plan and simulation model of urban drainage guarantees a good development.

Right: Without a plan and without a simulation modeli development decelerates (iDNES, 101222)

Aquion works on Master Plans of drainage systems (eg. Brutnál, CZ and Tatranská Lomnica, SK), on studies to improve particular parts of the drainage system (eg. Trutnov, Česká Skalice, Lysá nad Labem, Mladá Boleslav), on special tasks (evaluating function of inner and outer rain drainage system of new Depository of National Library of Czech Republic, proposals to eliminate the effluent of rain water on the floor of production halls of Model Obaly Opava). We are also designing anti-flood measures (Hartunkov, Svádovský potok), evaluating capacities of bridges (Klášterní Skalice after flood in 2013, new bridge at the planned by-pass road of Blatná). We are also developing our own software to simulate sewage and rainwaters systems SiteFlow. Information concerning software SiteFlow can be found in Czech at www.aquion.cz. If you have problems with urban drainage and you would like to be sure that proposed solution are correct, Aquion can help you.

Left: Levels in main sewage line to swith pumping from new retention reservoir off and on.

Right: Critical region before road roundabout 20-years 15 minutes design rain, green arrows water flows out of he sewer system. 

Left: Watersheds of combined sewer system          

Right: Types of surface

Example of proposed measures: red line increasing the capacity, green description – new constant slope, blue line – a new pipe.