Author(s): Eduardo Chavarri; Edwin Pino; Julio Kuroiwa; Walter Chuan

Linked Author(s): Edwin Pino

Keywords: Urban flooding; Rainfall - runoff simulations; Hydraulic modeling; Urban planning; Territorial management

Abstract: Tacna region, which is located in the northern end of the Atacama region, is a very dry area. Several creeks that showed no runoff for 88 years caused floods in several cities in 2015, 2017, 2019 and 2020. On February 21, 2020, unusual precipitation caused major runoff in Quebrada del Diablo (Devil´s Creek). This watercourse showed no runoff for more than 8 decades, and several crossings were built to connect National Road 38 with the Alto Intiorko sector. Several neighborhoods, roads, public buildings, and businesses of Tacna City were flooded causing 3 deaths and affecting 1945 families whose homes were inundated. Devil´s Creek encompasses 52.84 km2 and flows 24.3 km in the SW direction from the continental divide. Average slope of this watercourse is 5.1 %. Due to settlement in Tacna City, the creek´s mouth flows directly into the city. The February 2020 event was recreated using a semi-distributed hydrologic model and a 2D hydraulic model. In addition, several field trips were conducted to the area of interest. Preliminary results show that, even when unusually high precipitations were recorded in the area, the event itself did not trigger extensive flooding. It was observed during the field trips upstream on Devil´s Creek that two major road crossings, had been destroyed due to overflooding. None of them were not built by any local, state or national agency and one of them was, in essence, an informal embankment built by smugglers to avoid custom´s inspections near the Chile-Peru border. Runoff caused by precipitations was dammed in both crossings and they were overflooded, thus creating a dam break effect and causing extensive damage downstream. State agencies, such as the Geological, Mining and Metallurgic Institute of Peru (INGEMMET, acronym in Spanish) had already recommended resettlement of the affected areas in reports preceding the event but no action was taken as of 2020, when flooding occurred in Tacna City. Output from computer simulations and field inspections show that both creek crossings exacerbated the outcome of high precipitation in the area. Previous events had occurred in recent years and there had been warnings and recommendations to resettle population under imminent danger from national agencies. However, no major action took place. It was recommended to suppress any crossing that fully interrupts watercourses, particularly in medium to large basins and to resettle neighborhoods located near the creek´s mouth. Additional structural and non-structural measures were also recommended.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221674

Year: 2022