Estimating Wind Damage in Forested Areas Due to Tornadoes

Abstract

Research Highlights: Simulations of treefall patterns during tornado events have been conducted, enabling the coupled effects of tornado characteristics, tree properties and soil conditions to be assessed for the first time. Background and Objectives: Treefall patterns and forest damage assessed in post-storm surveys are dependent on the interaction between topography, biology and meteorology, which makes identification of characteristic behavior challenging. Much of our knowledge of tree damage during extreme winds is based on synoptic storms. Better characterization of tree damage will provide more knowledge of tornado impacts on forests, as well as their ecological significance. Materials and Methods: a numerical method based on a Rankine vortex model coupled with two mechanistic tree models for critical wind velocity for stem break and windthrow was used to simulate tornadic tree damage. To calibrate the models, a treefall analysis of the Alonsa tornado was used. Parametric study was conducted to assess induced tornadic tree failure patterns for uprooting on saturated and unsaturated soils and stem break with different knot factors. Results: A power law relationship between failure bending moments and diameter at breast height (DBH) for the hardwood species provided the best correlation. Observed failure distributions of stem break and windthrow along the tornado track were fitted to lognormal distributions and the mean of the critical wind speeds for windthrow were found to be higher than that for stem break. Relationships between critical wind speed and tree size were negatively correlated for windthrow and positively correlated for stem break. Higher soil moisture contents and lower knot factors reduced the critical wind speeds. The simulations show varying tree fall patterns displaying forward and backward convergence, different tornado damage widths and asymmetry of the tracks. These variations were controlled by the relative magnitudes of radial and tangential tornado velocities, the ratio between translational speed and maximum rotational wind speed and the mode of failure of the trees. Conclusions: The results show the complexity of predicting tornadic damage in forests, and it is anticipated that this type of simulation will aid risk assessments for insurance companies, emergency managers and forest authorities.

Unearthing Current Knowledge Gaps in Our Understanding of Tree Stability: Review and Bibliometric Analysis

“…Derechos are fast-moving lines of severe thunderstorms that generate straight-line winds, damaging trees and forests over significant distances. Non-synoptic storms such as tornadoes and thunderstorm downbursts occur at different scales and can produce high wind speeds resulting in significant localised treefall [147].…”

Forest Disaster Detection Method Based on Ensemble Spatial–Spectral Genetic Algorithm

“…Natural disturbances such as intense wind [4], wildfires [5], and drought [6] often cause severe ecological destruction and economic losses. Hurricanes and fires, two recurrent natural disturbances, can be severe, intensifying the harm to the forest ecosystem [7]. The global environmental trends model forecast a global canopy cover reduction of 223 million hectares by 2050 [8].…”

“…Divide pixels into three categories: D, U , and I, according to FCM and τ with ( 6) and (7) Calculate the fitness of each individual using neighborhood window with ( 8)- (11), which is restricted to uncertain regions. Uniform crossover in indefinite regions using P c .…”