Urban Growth and Flood Disasters in the Coastal River Basin of South-Central Chile (1943–2011)

Abstract

Abstract: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 ) 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.

A paleo‐hydro‐geomorphological perspective on urban flood risk assessment

“…Historical analysis of urban development is key for enhanced understanding of flood risk evolution (Cortès et al, ; Di Baldassarre et al, ; Di Baldassarre et al, ). Our results evidenced a lack of appropriate territorial planning and flood risk management that allowed the city to grow over flood prone areas including wetlands and paleochannels in agreement with findings by Rojas, Mardones, Rojas, Martínez, and Flores (); Rojas, Munizaga, Rojas, Martínez, and Pino (). Wetlands usually act as buffer zones mitigating the effects of floods and paleochannels serve as river corridors that attenuate the magnitude of extreme floods evacuating excess runoff and should therefore be protected (Spaliviero, ) and directly used for territorial planning.…”

Social Perception of Ecosystem Services in a Coastal Wetland Post-Earthquake: A Case Study in Chile

“…In general, it was observed that the regulating and cultural ecosystem services obtained a high valuation in terms of frequency of provision despite morphological, social, and environmental changes from the last earthquake. In fact, in the regulating services, the high recurrence of natural (tsunamis, floods) and anthropogenic disasters (fires) that affect the Chilean Mediterranean region [31,37,51] may have positively influenced the utilitarian valuation of the wetland by the population, as it forms part of the inhabitants' collective memory. This is not novel, and is consistent with Barbosa and Villagra [52] as wetlands are essential to mitigate the effects of such catastrophes, and are socially valued as spaces of recovery after earthquakes, especially if they provide biophysical attributes such as water [53].…”

A General Overview of the Risk-Reduction Strategies for Floods and Droughts

“…It is a commercial free software, and many studies have applied it for various purposes, not only limited to flood modeling but including sediment transport simulation and dam break, etc. (e.g., [55][56][57]). The newer version of HEC-RAS even extends its capabilities to two-dimensional inundation modeling [58].…”