Rehabitar la Montaña: strategies and processes for sustainable communities in the mountainous periphery of Medellín
Thousands of poor, marginal communities’ residents die due to landslide events every year. The quick urbanization of mountainous areas, combined with an increased frequency of landslide events induced by heavy rains due to climate change, is leading to increased deaths year after year, and the problem will only get worse. Landscape Architects, trained to analyze and intervene in situations with complex natural and social territorial dynamics, are in position to make positive contributions to mitigating risks in such situations. A collaborative effort between a team of landscape architects from Germany and Urbanists in Medellin Colombia is carrying out a four-phased research and implementation proposal to anticipate and mitigate risk in low-income settlements on Medellin's urban periphery. They propose five pilot projects to test risk mitigation strategies through monitoring and early warning systems, drainage improvements, urban agriculture, slope forestation, and developing sites with the supplied services.
A mathematical approach for assessing landslide vulnerability
A natural phenomenon (hazard) may be characterized in terms of temporal, spatial and magnitude probabilities. The effects of the interaction between the hazard and the exposed element depend on the intensity of the hazard and on the resistance, sometimes called susceptibility, of the element at risk, which describes the propensity of a building or other infrastructure to suffer damage from a specific hazard impact. Consequently, a modern concept of vulnerability must consider the intensity of the hazard as well as the structural resistance of the exposed infrastructure. This concept is referred to as physical vulnerability, and the most accepted definition is a representation of the expected degree of loss quantified on a scale of 0 (no damage) to 1 (total destruction). Thus, this work presents a mathematical model for landslide physical vulnerability assessment, here named the T-Model, based on the “Principle of Natural Proportionality” and calibrated with field observations of the massive rainfall-triggered landslide event that occurred in Nova Friburgo, Brazil in November of 2011. The model was also calibrated for a flow-type movement that is based on field observations of the failure of a tailing dam that affected the district of Bento Rodrigues, Brazil in November of 2015. The results showed a good agreement between predictions and the observed level of damages. Thus, it is possible to conclude that from a mathematical point of view, the model may be qualified as universal. It is recognized that a real universal objective model for vulnerability to landslides is not practical at present. More important than the model itself is the methodology that is presented here, which leads the user to take qualitative damage information from the field and develop it into a quantitative mathematical framework. Potential users of the T-Model must be cautious regarding the values of parameters that are presented in this paper. The T-Model is just a modest proposal that requires further calibration and deep expert criticisms.
Tools for Sediment Management in Rivers
Sediment management, including supply and continual redistribution of sediments for channel maintenance and channel forming, is critical for effective environmental water programs. Many tools have been developed to more effectively manage sediment in rivers for ecosystem maintenance and improvement. This chapter reviews some of these tools, including sediment mobilization theory, environmental water requirements for geomorphic maintenance, and complementary options. Sediment mobilization theory addresses entrainment, transport, and deposition of sediment particles. Environmental flows assessment approaches that support geomorphic processes include threshold-based approaches, field/laboratory methods, and holistic methods. Complementary options for sediment management include catchment-scale conceptual models and budgets for sediment, basin land management (e.g., reforestation, better agriculture practices, etc.), sediment management through dams, and sediment augmentation below dams. These complementary options often have cobenefits with other management objectives. The chapter emphasizes that sediment management is generally complex, such that continual research is needed, ranging from improved sediment mobilization models to large-scale river experiments.