Author: Silvia Franceschi - Andrea Antonello - Giustino Tonon - Francesco Comiti -
Contact name: Silvia Franceschi
Organization: Free University of Bolzano Italy
Sectors: Agriculture, Livestock and Fisheries - Environmental studies -
Software:
Situation:
In forested mountain landscapes wood can significantly increment the total flow volume during a flooding event. On the other hand, the presence of large wood on river sides has positive effects on hydrogeomorphological diversity of habitats and represents a source of organic nutrients in the water. Therefore a compromise should be reached in the management of vegetation (within river corridors and on connected unstable slopes) aiming to reduce flood hazard while preserving its function of large wood supply for river ecosystems.
Solution: The developed modules in JGrassTools and gvSIG evaluate the hazard derived from large wood transportation during flooding events following a simplified approach. Therefore, the implemented model is thought to support the application on large areas and with the minimum data availability.
The hazard is caculated considering the two main processes of the problem, recruitment of the logs from the hillslopes and transportation of the logs downstream, through the evaluation of:
- the effective presence and characteristics of the vegetation in the inundable river corridors for log requirement
- the characteristics of the flow in the stream network for the transportation of the logs downstream.
The vegetation information can be provided using a simplified model which evaluates the lenght and the volume of the logs using an experimental equation based on the information provided by the CHM and DTM, or using a detailed model of the vegetation based on an extracted dataset with the position and height of single trees.
The propagation of the logs downstream and the evaluation of the clogging sections are based on geometric and hydraulics parameters evaluated through an integrated 1D hydraulic model which implements the Saint Venant equations.
Benefits: This model for the evaluation of the Large Wood (LW) floods can be used for any river stream and with very usually accessible data, mainly derived from DTM.
Information on the presence, position and volume of the vegetation can be provided separately or can be calculated by the software based on the DSM and a map of forest stand.
The model is therefore scalable on space and adapted to different resolutions/details of the input data.
The final result of this model is the spatial identification of the clogging sections due to the transport of logs along a river network. This result represents the first step to identify the source of logs and the weakness sections of the network and therefore it represents an easy and quick way to start to face to the proble of natural hazard due to floods with woody debris.
Language: en
