The program LU-NA is used for the calculation of rainfall-runoff models, and river basin models. At present all well-established procedures are contained in LU-NA (among others: Lutz, SCS, Kirpich). Regarding the definition of flow hydrograph in FLUSS-2D as well as the consideration of surrounding areas in the calculation of channel networks with HYKAS an effective tool is available.
Basics of design
The program LU-NA determines the unit and flow discharge hydrograph of a catchment area with the rain events and area characteristic data. Discharges can be produced both from natural and from urban catchment areas.
For the respective catchment: size of the area, the PSI-value (the initial losses), the base flow and the time interval are required.
A temporal distribution of the standardized precipitation distribution can be determined by LU-NA. The program REGEN can be run after LU-NA. The resulting precipitation rain events can be obtained directly from LU-NA. For the determination of the effective precipitation, a time-dependent discharge is needed. In the simplest case this can be a constant process with initial loss or the PHI index procedure (without initial loss with constant loss rate). With a more sophisticated approach, LU-NA determines the run-off coefficient according to HORTON procedure (exponential course), or in accordance with the procedure of LUTZ.
For the computation of the unit hydrograph, different procedures can be selected. In detail, these are the regionalization procedure of LUTZ, The linear cascade storage, Double or Triple storage cascade, the double cascade storage after Wackermann/DVWK, the individual definition of the single ordinates or the KIRPICH procedure.
The discharge hydrograph curves of the rainfall-runoff-model, the discharge hydrograph curve of the constant discharge, the Lake-retention as well as the river basin model can in the programs HYKAS and FLUSS be transferred.
Constant Discharge
With the program LU-NA, the constant discharge can be computed. Here considering a discharge hydrograph computed before, a constant discharge is simulated. The output of the results are presented both in tabular and in diagram form.
Retention Curve
In water, it can be accepted that the flood levels of different flood events are not identical. For this reason a retention curve is provided, which is put as an envelope to the water levels of different flood waves. For the calculation of a flood retention area from a given discharge and/or hydrograph, the production of a retention curve is essential.
Lake-Retention
With the Lake-Retention, the computation of uncontrolled flood storage basin is possible. When using the Lake-Retention, the storage line and the discharge curve (bottom outlet and flood discharge) of the flood control storage basin are needed. Already small discharges can impound the basin. If the flood event is greater than the designed, usually the flood support area is not sufficient, the bottom outlet is used. The portion of the supply, which does not flow off through the bottom outlet into the underflow, is exhausted over the surplus disposal work.
River-basin Model
A river basin model exists usually of several individual well models for the respective partial catchment areas. Independend from the length of the water section and the size of the catchment areas, a well fitted and realistic illustration can be developed with LU-NA. Models for the wave deformation are considered along the waters course and the simulation of water retaining structures.
With the selection of the catchment areas (EZG) a distinction in EZG city, EZG country or EZG city/country can be made for a better overview. One will be assigned to each EZG in the rainfall-runfoff-model computed and/or discharge hydrograph curve.
A node is marked on a place in the river basin, at which a discharge hydrograph curve is to be produced. In the reality nodes are usually water gauge levels, constriction or discharge. Between two nodes, the affecting situations can be copied along the flow distance. Here it can be differentiated between storage models (Lake-Retention and Constant Discharge) and the wave deformation up to the nearest knot.
The wave deformation (flood routing) causes the movement and deformation of a flood wave produced from the river section or a storage reservoir flows.
The discharge from cultivated area, which is derived into the receiving stream, can be considered by storm overflow, storm overflow basin and rain retention basin.
At each node, the produced discharge hydrograph curve is available. The data can be exported alternatively in the ASCII or EXCEL format. For the output of the complete structure of river, basin model with short description is listed in table and the discharge hydrograph curve is represented graphically and tabular.
Data output
The computation results are presented predominantly tabular and graphically. After the computation, the results will be indicated automatically in a preview, where it can be rejected or printed.
Data exchange
| HYKAS | Computation of Duct system |
| FLUSS | Water level computation (1D and 2D) |