The Program REBECK-LZ serves as a confirmation for the ability of Storm water storage using a long - term continuum simulation as according to DWA - A 117 (04/2006). The long term simulation to the full continuum includes the dry periods as well. For all impounding events, the program indicates the starting time and the duration of the event, the maximum storage volume as well as the overflow and the storm volume. From the statistical analysis of all the events, the maximum storage capacity necessary for any return period is given.
The workability of the program becomes particularly effective if the sewage system data created by HYKAS and GraPS are used. Due to same database, the storm network data can be used by REBECK-LZ without further modification.
Basics of design
The calculation is different between the surface runoff model and transport model (Storm-Network model).
Surface runoff modell
In the runoff model, to calculate the initial losses (wetting and trough), different methods are used. The wetting losses are considered as threshold value and are deducted initially from precipitation. The trough losses are computed according to the limit value (boundary value) method .
For the infiltration of the permeable surface, the Horton method is used. This describes the changing infiltration capacity, from the initial infiltration rate to the final filtration as a function of time. It is assumed that during this period, the rainfall intensity is either equal or greater than the actual infiltration capacity. When the rainfall is less or dry areas, during which the rain intensity is smaller than the infiltration capacity, an extension of Horton approach by Paulsen is used.
Unlike the storm water calculation with the single rain event, the evaporation in the long-term simulation plays an important role, where dry periods are also considered. Actual evaporation data over longer periods, however, are much less likely than long-term series of rain events. Moreover, they are almost invariable in terms of daily values. For these reasons, a long-term simulation with the measured evaporation data is almost impossible. In REBECK-LZ a yearly variation of the mean daily evaporation is used, which can be modified per hour. The computation of the evaporation takes place only in dry periods. During rainy season, the evaporation is relatively less in amount & is therefore not considered.
Transport model
The inflow hydrograph curve of the individual sewer reach, computed by surface runoff model, is overlaid by the transportation model and the temporal distribution along the flow path is computed. For the long term simulation, using the hydrodynamic models with the solution of the continuity equation and momentum equation is very time consuming. So in REBECK LZ, the kinematic wave equation is used, which permits a time step within a minute range. With this basic approach, the outflow waves can be produced only downwards. Thus the underwater conditions do not have influence on the computation of the surface water and the back pressure above the up-to-date are not considered. In the case of impoundage the water quantitity not transported is stored in a fictitious reservoir. Only when the outflow is less than the maximum capacity Qvoll , the reservoir is made empty. The pressure water conditions with the reservoir are not specially treated. In the case of a back-up, it is accepted that all overflowing water quantities flow later again into the net. in addition, it is presumed that no any channel with counter-slope is present.
Application limitations
In a project can be
| • | Max. | 10,000 | pipelines |
| • | Max. | 200 | features |
| • | Max. | 100 | Profile types (Teilfüllungstabellen) |
| • | Max. | 50 | open outlet |
| • | Max. | 50 | Weir |
| • | Max. | 50 | Pumps |
| • | Max. | 50 | Stormwater storage |
| • | Max. | 50 | Main and/or side openings |
to be sized and stored.
Data exchange
The following Rehm programs use the same databse as REBECK-LZ:
| KAREL | Channel information system |
| GraPS | Graphical planning system for Sewer and Water Supply nets |
| HYKAS | Computation of Duct system |
| MENKOS | Quantity and Cost estimation |
| WERT | Property valuation for Sewage Network |
The program supports the ISYBAU-Format K (Storm water standard data). All input data can be read in and/or exported also over freely definable ASCII file formats.