IVU Umwelt GmbH

- GIS-Based Flood Modelling

0

The hydrologic model floodFILL is an easy-to-use system for calculation the spatial and temporal extent of an inundation in a floodplain.

floodFILL may give solutions to the following problems: 

What areas are going to be flooded in what amount of time?

What is the level of inundation in the areas flooded?

Do I have the appropriate data available to model the flood event?

The water enters the floodplain according to a given discharge hydrograph at an inflow point defined. Starting at that location the water volume is distributed stepwise into the floodplain corresponding to information extracted from the digital elevation model.

floodFILL is available completely integrated within the geographic information system (GIS) ArcView. Because of its limited number of  input data and the flexibility and adaptability floodFILL suites as well for Operational Support in real-time during a flood as for preliminary risk analysis of flood events and the precautionary assessment of potential damage of an inundation.

An urbanised floodplain is structured by man-made features such as road dams, embankments, etc., into a series of basins. These basins act as storage cells when flood water enters the floodplain. The timing and extent of flooding is determined by the volume and interconnection of these cells.

floodFILL employes a digital elevation model to determine the location, storage volume and interconnection of the storage cells. These storage cell's properties primarily control the temporal and spatial distribution of the water. Starting from the inflow points the model allocates the water entering the floodplain into the storage cells identified. 

Advantages:

  • data driven model
  • small effort in pre-processing
  • no calibration necessary
  • very fast calculations
  • scenario calculations
  • integration in any desired GIS
  • unlimited inflow points 
Inflows from e.g.
  • embankment breach
  • rainfall
  • sewage system
  • piping
  • groundwater 
Outflows into e.g.
  • sewage system
  • pipin

The core of the floodFILL model is built of a spreading algorithm based on a digital elevation model.

A digital elevation model, the location of inflow points and inflow flow rates or spillway design flood are required as Input data.

Furthermore, hydrological parameter are derived from the digital elevation model by the means of a GIS. The following figure illustrates the working flow within the pre-processing.

The inflow will be received via an integrated preliminary module. The module may be easily adapted according to different available data.

floodFILL calculates both inundation areas and flooding depths in the terrain and water levels and water volumes in the storage cells for the time steps given. Partial results are already available while the calculation is running.

floodFILL requires digital elevation data in grid format and additional break lines (lines containing surface features). Grids featuring required hydrological parameter are derived from the digital elevation model.

The input grids for the spreading model are created using the GIS ArcView. The model processes ArcView Grid files in any desired resolution.

The resolution of the digital elevation model depends on the problems under consideration and computer hardware capacities.

The processing of the elevation data and the derivation of the hydrological parameter has only to be repeated in case of any change of the terrain surface, e.g. additional breaklines due to a dam construction.

The model control is completely integrated into the geographic information system ArcView. The pre-processing of the input data, the calculations and the post-processing of the results can be managed using the GIS' wide range of tools for data analysis and result representation. Thus, all tools available by default and  functionalities additionally programmed are provided within a well-known and uniform user interface.

Operational support in emergency management

The system floodFILL perfectly works as a supporting tool in emergency management.
The high temporal and spatial resolution of single calculation time steps connected with calculations carried out very fast, helps to achieve prompt reactions in planning of evacuation measures and active damage defence (sandbag barriers, moving valuable things in higher storeys, etc.).
 
Important operational information referring to time and space will be available when integrating the calculated flooded areas with other information like infrastructure, e.g. in what time a street required for evacuation purposes is getting to be flooded and disrupted.

floodFILL facilitates the analysis of consequenceson the distribution  of water in the terrain when using artificial barriers. Effective positions of preventive measures, e.g. mobile protection barriers, can be determined for both precautionary planning and the case of an emergency.

The following figure illlustrates the result where two scenario calculations with and without an integrated artificial barrier had been carried out and compared.

Using floodFILL embankment breach scenarios along flood-control works can be calculated. The entered water volumes may be derived from e.g. water levels or design floods.  
Flood probabilties for endangered zones can be stated according to flood probabilty of a flood event. Thus, embankment points failing would result in severe consequences are possible to be identified.

In case of the availability of land use and infrastructure data, using empirical relations (to be established) between flooding depth and extent of damage it is possible to estimate the monetary loss to be expected.
 

Possible Scenarios:
  • Identification of potential dam spillways (Hot Spots)
  • Calculations for a embankments's well-known weak points
  • mobile protection barriers
  • river defence works to be planned
  • Estimation of potential damage

Customer reviews

No reviews were found for FloodFILL - GIS-Based Flood Modelling. Be the first to review!