Silvilaser 2019 - Poster Presentations »
Topographic Wetness Index from LiDAR Terrain Model Helps Forest Roads Maintenance
One of the main uses of a LiDAR survey is to obtain High Resolution Digital Terrain Models (DTMs). These models are essential in geomorphological and hydrological studies, which assist in making decisions about planning, operation and sustainable forest management. Since water is the main erosive agent, it is essential to study the impacts caused by it to help the adoption of soil conservation practices. In this context, the Topographic Wetness Index (TWI) allows the study of the effect of the terrain on water behavior. One of the components of forest production most affected by water is roads, as they have a surface that favors surface runoff. Mountainous reliefs are aggravating this situation, because the water velocity is proportional to the slope of the terrain, which causes greater recurrence of maintenance. Therefore, the objective of this work was to test the use of TWI in the identification of areas suitable for the accumulation of water in forest roads in order to optimize the maintenance survey in them. The DTM generated by the LiDAR survey at a forest site was processed in the SAGA GIS software, generating two variables: slope and catchment area that served as input to generate the TWI raster file. Using the ArcGIS software, the TWI values were filtered only for site roads. Twenty points of possible water concentration were visualized to obtain the minimum value of TWI that represented the risk of erosion. From this value, it was possible to determine for the whole area the critical regions that would need to be surveyed in the field. For the validation, all the regions needed for maintenance were identified in the field for comparison with the data obtained by the model. In the study area, the TWI values ranged from 0.59 to 21.97 and the critical points evaluated presented values higher than 9.0, which was the limit for determining the critical regions. With this, it was verified that only 7% of the area of roads present values higher than the defined limit. In addition, all the regions indicated in field for maintenance were foreseen by the model. It is concluded that the TWI model is a good support tool in the operation of forest roads, directing the surveys to points that are likely to require maintenance, significantly reducing the area of survey in the field, streamlining the process and optimizing resources.