Performance of the HAND model in mapping the areas susceptible to flooding using high-resolution spatial data

ABSTRACT

Mapping areas susceptible to flooding is an important step to minimize the damage caused by floods, especially in urban areas. This mapping is used to establish guidelines for use and occupation of the soil and in the formulation of civil defense plans. In the municipalities of Blumenau and Brusque, flood stricken areas were mapped, from surveys carried out after the events. From the topography represented in digital terrain models (DTM), the HAND model had been preliminarily applied to predict potential flood areas. Recently a new concept was introduced in contours above the nearest drainage (HAND contours), demonstrating the specific ability of this method for use in hydrological risk area assessment. This study aimed to evaluate more widely the performance of the HAND contour method in mapping areas susceptible to flooding, based on topographic surveys available for the municipalities of Blumenau and Brusque. The evaluation used the variables accuracy, omission and commission, and the parameters F statistic, overall accuracy, Fit (%), false alarm rate (FAR) and the trend rate (BIAS). The results showed that for floods of small magnitude, the HAND model overestimates the area susceptible to flooding. As the flood level increases, the HAND model performance improves. For the largest simulated flood of Brusque and Blumenau, the omission (missing area) was of 7.5 and 4.7%, respectively. The commission (surplus area) was 35.3 and 42.2%, respectively. Comparison with other studies shows that the performance of the HAND model is similar to those obtained by other authors with hydrodynamic models, which have a high demand for data input.

Keywords:  Environmental vulnerability; Mapping of risk areas