Influence of the El Niño Phenomenon on Shoreline Evolution. Case Study: Callao Bay, Perú

Abstract

Analyzing the long-term behavior of the coastlines in the vicinity of river mouths and estuaries usually relies on the mean (predicted) values of the sediment discharge from the river. However, this approach does not consider low frequency, severe events, such as El Niño (EN), that can have a large effect on coastlines. While the effects of an EN on flooding and droughts are well studied, little information exists about its effects on coastal zones, and especially on the evolution of coastlines. In early 2017, an EN occurred in the equatorial Pacific Ocean, and the country of Peru was affected with high precipitation levels, and extreme river discharges and flooding. During this event, in the district of Lima, the Rimac River discharged a huge amount of sediment into the Callao Bay, and the shoreline accreted approximately 1 km, demonstrating the significant effects that an EN can have on coastal zones. To explore these effects, this paper studies the influence of an EN on shoreline evolution in the Callao Bay by analyzing Landsat images from 1985-2019 to understand the shoreline evolution and identify changes to the coastline. Results show that when an extraordinary EN occurs (e.g., 1982-1983, 1997-1998, and 2017), the shoreline experiences high accretion compared to when a smaller, or no EN occurs. During these events, a significant delta forms at the south end of the bay, and the redistribution of the accumulated sediment by wave action causes the accretion of the adjacent coastlines for as far as 7 km north of the river mouth. This shows the importance of these events for the wellbeing of coastlines adjacent to river mouths affected by EN.

Millennial variability of terrigenous transport to the central-southern Peruvian margin during the last deglaciation (18–13 kyr BP)

“…2a and Fig. 5a) associated with local high fluvial discharges in Callao during the 2017 Coastal El Niño (Guzman et al, 2020) corroborates the use of variations in the abundance of fine particles as an indicator of fluvial inputs. These results are consistent with the grain size of fine particles (~ 6-14 μm) in marine cores associated with river inputs reported in different areas of the world (e.g., Stuut and Lamy, 2004;Stuut et al, 2007;Beuscher et al, 2017).…”

“…However, during summer there is an increase in river discharges associated with increased monsoon precipitation in the Andes (Garreaud et al, 2009;Vuille et al, 2012). Occasional floods occur and higher sediment discharges are associated with intense precipitation during extreme El Niño events (Bourrel et al, 2015;Morera et al, 2017;Rau et al, 2016;Guzman et al, 2020).…”

“…Using this methodology allows us to discriminate the different sources of terrigenous input, reconstructing the variations of fluvial and aeolian inputs dependent on changes in precipitation and winds intensity. On other hand, surface sediments were collected for grain size analyses during normal conditions and during the Coastal El Niño (April 2017, the latter characterized by increased river discharges (Guzman et al, 2020) and variations of surface winds in Peru (Echevin et al, 2018). These observations allow us to understand the effect of changes in precipitation and winds on grain-size distribution during periods of different climatic conditions.…”

Fires, floods and other extreme events – How watershed processes under climate change will shape our coastlines

“…One of these examples is observed at the Rio Rimac of Peru (Fig. 1), which discharges exceptional amounts of sediment to the coast during years of high precipitation (French and Mechler, 2017;Guzman et al, 2020). During these wet years, the shoreline at the river mouth progrades 100s of meters seaward, resulting in a river mouth delta with several distributary channels (Fig.…”

Increased El Niño amplitude during the last deglacial warming

“…During El Niño events, especially those with high sea surface temperature (SST) anomalies in the Eastern Pacific (EP), strong thunderstorms and precipitation occur on the coast 5,29,30,31,32 . These events produce catastrophic flash floods and large discharge of sediments during a few days 33,34,35 .…”