Beachfront Owners Perception of Beach Erosion along an Armored Shoreline in Southern Brazil

Abstract

Brazil has about 8500 km of coastline that is mostly undeveloped. However, the pressure of fast-growing coastal urban centers is already impacting the shore. This paper characterizes shore protection works in Hermenegildo Beach, evaluates their efficiency to protect property against the impact of storm events, and presents the response of beachfront owners to erosion. Hermenegildo is a beach village located 12km north of the border with Uruguay in Rio Grande do Sul, the southernmost state in Brazil. Several factors contribute to beach erosion in Hermenegildo: storm surge, redistribution of wave energy, rising sea level, the presence of an underlying layer of impermeable peat, and human activities. The shoreline is heavily armored with about 61% of beachfront houses protected by revetments (30%), seawalls (18%), or a combination of both (13%). A strong storm struck the Rio Grande do Sul coast in 16 April 1999 and resulted in severe beach erosion and destroyed 22 houses, besides all concrete structures, half of the quarrystone revetments, and 80% of the timber seawalls. Shore protection structures in Hermenegildo are threatened by erosion because: (1) they were built too close to the water, (2) shoreline retreat has been observed, and (3) armoring has reduced beach width. Most of the beachfront owners are aware of the severe beach erosion problem and appear to understand basic coastal dynamics. About 82% of the interviewed beachfront owners lost property due to erosion; 88% subsequently built protection structures to prevent further loss. Surprisingly, 88% of those who did not experience property damage also built defense structures. Armoring is commonly an initiative of beachfront owners who build low-budget structures without consultation by technical experts.

Long- and Short-Term Coastal Erosion in Southern Brazil

“…Destruction of coastal structures during storms has been a strong source of evidence of erosion in Hermenegildo. Beachfront owners have built seawalls and revetments to protect their properties from wave attacks and storm surges and yet have seen destruction not only of the armouring but also of the houses that were supposedly protected (ESTEVES et al, 2000a).…”

“…Studies addressing the occurrence and impact of storm surges in Brazil are scarce and limited to the monitoring of individual events. A few examples are the storms of July 14, 1993and April 19-21, 1995(CALLIARI et al, 1998b), April 3-5 and 24-26, 1997(BARLETTA et al, 1999), and April 16, 1999(ESTEVES et al, 2000a. The 1993 and the 1999 storms were very similar and consisted of extratropical cyclones formed after the passage of a cold front striking the Rio Grande do Sul coast with average wind velocities of about 75 km/h, resulting in a storm surge of 1.3m and 0.8 m (measured at the Rio Grande Port), respectively.…”

“…TOMAZELLI et a l., 1998;DILLENBURG et al, 2000) and the short-term (i.e. CALLIARI et al, 1998a,b;ESTEVES et al, 2000a;TOLDO et al, 1999). The increasing interest in coastal processes and shoreline changes reflects the intensification of coastal occupation and beach use, as well as the growing economic importance of beach-related tourism.…”

Erosão De Dunas Sob Ação De Um Evento Extremo De Alta Energia De Ondas Na Costa Central E Sul Do Rio Grande Do Sul, Brasil

“…Nas demais localidades da costa central e sul do Estado, a urbanização defronte ao mar é pontual (ESTEVES, 2004), remetendo a trechos de até 2 km de orla urbanizada. Questões locais relacionadas à falta de um planejamento mais adequado respeitando as feições geomorfológicas locais são ocorrentes, refl etindo em problemas ambientais nos balneários do Hermenegildo (ESTEVES et al, 2000), Mostardense e Praia do Farol (SIMÕES, 2015; SIMÕES, 2018) e balneário Mar Grosso (CUNHA, 2013). Nestes locais a ocupação foi introduzida em meio a dunas móveis próximo da linha de costa.…”

“…O balneário do Hermenegildo (33°39'59''S; 53°15'35"W) tem histórico relacionado com a erosão costeira (KOERNER et al, 2013. Estruturas de contenção a erosão já são colocadas há algumas décadas, e sofrem incremento a cada ano (ESTEVES et al, 2000; OLIVEIRA e KOERNER, 2015). A praia varia de dissipativa a intermediária (PEREIRA et al, 2007).…”