DHI Spain have just finalised an inundation study for the Spanish company - Llorens Fornes S.L, in the province of Valencia. The objective of the study was to investigate if a specific area, in the village of Masalavés, would inundate when considering three different return periods, T=25, T=100 y T=500 years. The results and conclusions are to be used as part of the zone re-classification process (rural to urban).
Figure 1: The study area with indication of the city of Masalavés and the river Júcar.
As shown in the figure 1, the inundation is caused by a combination of two factors, on one hand the local rain, and on the other the overflow from the river Júcar.
The model was configured with the river Júcar incorporated as an open boundary, and the local rain introduced via the “new” facility in M21 version 2007 called “rain on land”. The facility enables a simple hydrological modelling consisting of basically 2 parameters; precipitation and evaporation, which can be defined as constant, time series, or map (2D). Additional factors such as infiltration, run off coefficients etc needs to be incorporated into one of these two parameters.
But although its simple its very useful for modelling flooding of areas without clearly defined flow-ways, as was the case in the present study.
Figure 2 shows the results of the model simulations with and without the local rain for a return period of T=25 years.
Figure 2: Results of the T=25 year rain event simulation (Max water levels). The red area is the area investigated. Left: Without local rain; Right with local rain.
The results shows that the local rain plays vital role in mapping the flood risk areas, and future that it would be quite a task to model each of the streams with an 1D model using the traditional cross sections and a pre-defined river network delineation .
The conclusion was that the area in question was not located within a flood risk zone, considering the three return periods.