Estimates of tree canopy loss as a result of Cyclone Monica, in the Magela Creek catchment northern Australia

Severe tropical Cyclone Monica impacted the coast of northern Australia in April 2006 with estimated maximum wind gusts of 360 km h⁻¹. It rapidly moved inland losing intensity and passed over the town of Jabiru as a category 2 system, with maximum wind gusts recorded at 135 km h⁻¹. The cyclone had a significant impact on the landscapes within the Alligator Rivers Region and significant windthrow of trees occurred. This paper describes the level of impact that category 2 level winds had on tree canopy loss 10 days after cyclone and then again 1 year later. Recovery was assessed using multispectral satellite imagery in sub-catchments of the Magela Creek catchments. A non-linear relationship was fitted between a modified vegetation index (derived from Landsat TM5 satellite data) and percentage tree canopy cover (measured from very high resolution QuickBird satellite data). The results of the non-linear relationship, used to estimate percentage canopy cover, indicate that 10 days after cyclone, there was significant disturbance to tree canopy. However, data 1 year after cyclone show that recovery of canopy across the studied catchments varied between 8% and 19% of the percentage canopy cover that remained after the initial impact of the cyclone. Further analysis in the three sub-catchments using Geographical Information System showed that proportionally, riparian zones and inundated areas in each of the sub-catchments suffered greater loss of tree canopy cover compared with upland areas.