Search Results (5)

In recent decades, the interplay of several factors, including land use change (particularly urbanization) and global warming, has resulted in harsher flooding, often associated with geomorphic disruption. These events in Latin America are predominantly driven by the El Niño Southern Oscillation (ENSO) phenomenon. The Andalién River basin is no exception, with a notable incident occurring in July 2006. This reality points out the need to study the geomorphological behavior of rivers. Geomatic tools can contribute to address this issue, thereby improving the planning and management of water courses. This paper presents the assessment of the morphological evolution of the Andalién River, downstream to the city of Concepción in a period of 75 years (1945–2020), in response to changes in land use and anthropogenic interventions on the river itself. Based on temporal satellite imagery and historical aerial images (from 1945 to 2020) combined with digital elevation models (LiDAR and TamDEM-X data), morphological alterations are revealed, which were caused by urbanization and anthropogenic activities. We demonstrate how the South River Toolbox (SRT), an original GIS tool developing in QGIS (in-house), enables the extraction of key geomorphological features of a river and their analysis, including their time evolution. This retrospective analysis includes an innovative method and tool to measure the lateral migration rate of the active channel. Ultimately, this study provides valuable insights for future management strategies, offering a comprehensive basin-level analysis of the Andalién River and a cartographic framework to aid decision-making, planning, and management of the fluvial corridor. Full article

Climate change scenarios predict alarming levels of water scarcity and damaging flood events worldwide. Considering hydric systems in integrated spatial planning will be crucial in mitigating, adapting, and reversing climate change’s catastrophic effects. This paper focuses on fluvial restoration as part of urban and territorial regulatory frameworks in the Andalién River and the city of Concepción in Chile. We consider three work scales: (i) basin, (ii) river reaches which focus on the city–river interplay, and (iii) site-specific, deepening the discussion around the last two. The objective is to elaborate an interdisciplinary dialogue between urban design, fluvial dynamics, and the Chilean regulatory framework where property rights play a predominant role in the management of natural resources (water and land). In this regard, the ‘New Latin American Constitutionalism’ offers concrete possibilities to operationalize an emerging paradigm that recognizes legal personhood for Nature. The incorporation of an ecological function to property rights emerges as a new way in which the principles of resilient urban development can be applied in order to combine river dynamics and urban growth. Full article

Several impacts over ecosystem services have been produced by land use/cover changes, placing it as one of the main factors driving global environmental change. In the present study, the SWAT model was used to assess the effect of land use/cover changes on the hydrology response in the Andalien river basin from the south-central zone of Chile. Three land use/cover scenarios (LU_1986, LU_2001, and LU_2011) were compared over a period of 30 years (1984–2013) to remove the effect of climate variability on hydrology. The results show a significant decrease in total annual flows among the three LU scenarios. The greater differences in the annual flows of 25.05 m³/s were observed between LU_1986 and LU_2011 scenarios. The hydrological cycle dynamics in the basin show an increasing trend of evapotranspiration and surface flows with a significant decrease in percolation and lateral flow on a monthly and seasonal scale. This behavior can be explained by the increasing percentage of the basin area covered by exotic plantations, from 35.22% to 63.93% during the period. The evidence of these changes and the evaluation of their effects are particularly relevant for the long-term sustainable management of water resources. Full article

Coastal floods have become a serious problem on a global scale, increasing in frequency or magnitude due to natural conditions, and exacerbated by socioeconomic factors. This investigation analyzes the role of tides and average sea levels on the development and intensity of flooding in the lower section of the Andalién River, located toward the southern extreme of the coast of central Chile and northeast of Concepción, the country’s second most populous city. Numerical simulation (1D) was used in five modeled scenarios to determine potential flooding areas, demonstrating the influence of tides in flooding processes as far away as 7.3 km from the river mouth, which is reinforced by the fact that 57% of flooding events occur during syzygies. Further, a climate change-induced sea level rise of 60 cm from current levels by the end of the 21st century would produce a 4% increase in flood-prone areas, with 17% of flooding affecting the current built-up area and 83% of floodplains and salt marshes. Efforts must be made to protect or conserve these latter areas in order to increase natural resilience, given the high costs of implementing structural measures to protect future residential areas. Full article

Urban flooding is an increasing problem in developing countries, thus understanding flood dynamics is necessary to establish guidelines on urban development and flood management. This paper studied the lower reaches of the Andalien River basin, situated on the coast of the Greater Concepcion Metropolitan Area (CMA), the second most urbanized area in Chile. This basin experienced a record 21 flood events in the last 50 years. Patterns in the evolution of urban growth were evaluated using a historical analysis (1943–2011) that specifically focused on how these patterns interact with zones that are prone to flooding over different return periods. Our model applied to the CMA, but is sufficiently transversal to be applied in similar areas. It was determined that the built-up area increased by 1457 ha and had an urban form vulnerable to future flooding due to its location on landforms exposed to flood risk, with altitudes of <8 m and slopes of <0.5°. The bankfull channel of the Andalien River lost 18.4% of its area. Upstream, management of the river decreased smaller floods for a return period of two, five, and 10 years; however, for a return period of 500 years, risk remained at high levels. These findings help to rethink and improve urban planning and the response of Chilean cities in relation to flood hazard. Full article