Wave runup estimations on platform-beaches for coastal flood hazard assessment

Abstract

Wave runup in a shore platform environment has been acquired by in situ measurements at high tide and along field debris following the December 6, 2010, flood near Rimouski (Quebec, Canada), south coast of the St. Lawrence estuary. Using offshore wave data and beach slopes, a linear empirical runup relationship has been adjusted to the study site and showed good predictive results. Two types of beach slopes, the upper foreshore and foreshore slopes, have been assessed in order to calculate the surf similarity parameter. It appears that the foreshore slope, located between the coastline and the end of the foreshore at the seaward edge of the platform, shows best results. This slope was thus used to calculate the wave runup on the shore platform. A static flood map, adding wave runup to observed peak tidal level including the storm surge during the December 6, 2010, flood, has been realized on a LiDAR base layer for a specific site in Sainte-Luce. A second flood map has been applied to validate the approach on an external site in Sainte-Flavie, outside the study area. In both cases, predicted flood extents highly correspond to observed flooded area. High underpredictions occur when using the observed storm tide level only (a 182-year event) without runup, where only 5 and 4 % of the studied area are considered as flooded, respectively. It appears that in a shore platform environment, a wider foreshore reduces wave runup and flood levels.

Multihazard simulation for coastal flood mapping: Bathtub versus numerical modelling in an open estuary, Eastern Canada

“…Despite some studies on static sea level scenarios for coastal flood assessments in Nova‐Scotia (McGuigan, Webster, & Collins, ; T. Webster, McGuigan, Collins, & MacDonald, ), Prince Edward Island (T. L. Webster, Forbes, Dickie, & Shreenan, ), New‐Brunswick (T. L. Webster, Forbes, MacKinnon, & Roberts, ) and the province of Québec (Bernatchez et al, ; Didier et al, ; Didier, Bernatchez, & Marie, ; Didier, Bernatchez, Marie, & Boucher‐Brossard, ), the coastal population of Eastern Canada still lacks proper flood maps that are validated with nearshore dynamics, including waves and water levels. Apart from accelerating sea level rise (Barnett, Bernatchez, Garneau, & Juneau, ) and sea ice shrinking and increasing storm impacts during winter in the St. Lawrence (Senneville et al, ), the future wave climate is expected to become a major capital forcing affecting coastal flooding in the next decades (Ruest et al, ).…”

Nonhydrostatic and surfbeat model predictions of extreme wave run-up in fringing reef environments

“…swash) [1,2]. Its accurate prediction is essential for the effective design of coastal structures, beach nourishment planning and for predicting the extent of damage associated with storms [3,4].…”

Modelling Coastal Flood Propagation under Sea Level Rise: A Case Study in Maria, Eastern Canada

“…In Canada, the probability of exceeding a specific storm intensity within a certain period of time is commonly associated to a static intensity-duration-frequency (IDF) curve for a given hazard (e.g., river flooding, coastal flooding), without considering climate change [91]. In coastal areas, this often means neglecting the effect of climate variability on nearshore dynamics, such as wave runup and wave climate [19,92].…”

“…In the Estuary and Gulf of St. Lawrence (EGSL), virtually 35% of the coastline is considered as low-lying [18]. Moreover, coastal infrastructures are often built not more than 2 m above the higher high water level [19,20].…”

“…On 6 December 2010, when an extratropical storm hit Atlantic Canada (Québec, New-Brunswick, Nova-Scotia, Prince Edward Island), severe damages to houses and coastal defenses [21] have been mainly associated to high water levels due to the storm surge [22,23]. Theoretically, the return period (RP) of this event, in terms of water levels only, has first been estimated to be >180 years in Rimouski [19]. In Maria (Chaleur Bay, Gulf of St. Lawrence), the estimated RP of the total water level and wave runup was higher than 100 years [20].…”