Os processos geomorfológicos relacionados a fluxos de detritos são os mais catastróficos da natureza devido à sua alta velocidade, energia cinemática e grande volume de sedimentos mobilizados. Os danos e os prejuízos econômicos provocados por este movimento têm sido significativos para vidas humanas, terras agrícolas, assentamentos e propriedades. Portanto, é essencial compreendermos as características das áreas fonte e áreas de deposição para planejar a mitigação de desastres. Índices morfométricos na escala de bacia são bastante úteis para compreender a iniciação, propagação e deposição de fluxo de detritos, melhorando a avaliação da suscetibilidade e geração de mapas de perigos. Este artigo caracteriza os índices morfométricos nas áreas que ocorreram os fluxos de detritos que afetaram quatro bacias (Cuiabá, Príncipe, Vieira e D’Antas) situadas no reverso da Serra do Mar fluminense. Os índices incluem o Ângulo de Encosta, Índice Topográfico de Umidade (ITU), Índice de Potência Unitária de Corrente (IPUC) e Fator Topográfico (LS). Os índices morfométricos foram derivados de modelos digitais de terreno (12,5-m de resolução) usando ambiente de Sistema de Informações Geográficas. Os resultados mostram que o fluxo de detritos foi deflagrado em amplitude >1.200 m, Ângulos de Encosta >45°, por escorregamentos nos taludes laterais ou na cabeceira de drenagem e desenvolvidas no canal principal com valores altos de ITU, IPUC e LS. Os fluxos de detritos foram depositados em Ângulos de Encosta <2° em bacias com altos valores de ITU e IPUC (exceto Príncipe e Vieira) e baixos valores de LS. Portanto, os índices indicaram as classes críticas para a ocorrência das fases de fluxos dos detritos das bacias analisadas.

&lt;p&gt;Gully is an issue of the climate crisis in most coastal areas of the world. More than 70% of the world&#039;s sandy coastlines would be eroded in recent decades. Anthropogenic climate change is one of key factors controlling soil erosion occurrence. Soil erosion control is extremely important for soil conservation work and territorial planning. The municipality of Nacala, province of Nampula, Mozambique, has gully susceptibility as a known problem. The Japan International Cooperation Agency (JICA), concerned about the intense urban erosion in the Nacala region, which causes problems not only for the population living in critical areas but also for the proper functioning of the Nacala Port, has been making efforts to identify the causes and mechanisms of the phenomenon and suggest corrective and preventive measures covering the area of the Mocone basin, Nacala. Thus, we obtained information on the causes and mechanisms of evolution of these phenomena to allow the joint search for the features that determine the natural susceptibility to erosion of the municipal territory. We also identified that the soil type in the Mocone basin is sandy-clayey, with an infiltration capacity of 50mm/hour, erodible, with a drainage network mainly characterized by rills and gullies, with periodic surface runoff, only during heavy rains. Our studies indicated a catchment with a significant area upstream of the erosion process (2.34 km&lt;sup&gt;2&lt;/sup&gt;). The maximum project flows obtained in the our preliminary hydro-meteorological studies, considering intense rains with a return period of 100 years, and with duration equal to the time of concentration of the catchment basin (90 min), also proved to be quite significant, with values above of 25 m&amp;#179;/s. Accelerated erosion in this location seems to occur, preferentially, in sectors where those natural factors have been exacerbated by anthropic factors due to inadequate occupation of the physical environment. This urbanization resulted in waterproofing, an increase in surface runoff volumes and a reduction in the concentration time of this basin. In addition, the rainwater drainage of some streets was released directly into the natural terrain, without the proper hydraulic works to reduce energy. The rapid development of the erosion branch towards the Nacala Port proves this close relationship between inadequate urban drainage and the evolution of the analyzed erosion process. The results obtained also prove, once again, the importance of analysis and mitigation approaches for large scale erosion processes that contemplate the catchment basin in its entirety, where erosion control practices or changes in soil cover are necessary.&lt;/p&gt;

Following a small landslide, a large landslide or rockslide occurred on the left (western) slope of the Garcia River, southern Blumenau (Santa Catarina state Southern Brazil) at about 2 : 00 am on Friday, October 23, 2015. The landslide appeared to be controlled by the high-intensity rainfall of 80 mm/2 days and duration rainfall of 354 mm/month in addition to unfavorable geological and geomorphologic settings. Landslide debris destroyed 4 houses at the base of landslide slope and completely dammed the Garcia River with a crest height of about 6.0 m above the streambed. Shortly after the landslide dam formed, the dam was filled completely with water and subsequently failed due to overflow and erosion. By the time of our site visit, the Garcia River has been partially blocked with an estimated water level of about 4.5 m above the streambed, creating a small potential for flash flooding and debris flow at the blockage. On December 3 to 4, 2015, Japan International Cooperation Agency (JICA) carried out an on-site survey, in response to the request of the Department of Geology and Natural Risk Analysis of Blumenau Municipality. The objective of the technical survey was to analyze the risk of landslides and provide some geotechnical recommendations for emergency measures and restoration countermeasure works relative to landslide dam.