Maria del Pilar Cornejo-Rodriguez

Urban flooding is a major problem in many coastal cities around the world, mainly caused by factors such as poor urban planning, outdated sewer capacity or high frequent extreme events. In developing countries such as Ecuador, lack of monitoring, financial constraints and absence of proper policies exacerbate flooding problems. The use of the Stormwater Management Model (SWMM) helped to identify zones that are flooded even with a 2-year precipitation event at Duran city. Since there are no flood monitoring stations across the study area, model calibration was performed against unofficial records (people complaints, media photographs, and water marks on walls). Model results fairly agreed with those unofficial record. However, a validation process is not achievable yet due to lack of enough flood data even in flood prone areas. To further increase city resilience, authorities and stakeholders should engage in climate actions to raise flood hazard-risk awareness, monitoring hydro-meteorological factors, complement drainage operations with nature-based solutions, and improve hydrodynamic modelling to develop a flood early warning system for the city.

Duran is a coastal city located in the Guayas Estuary region in which 24% of urban sectors suffers from the effects of chronic flooding. This study seeks to assess the causes of Duran’s vulnerability by considering exposure, population sensitivity and adaptive capacity to establish alternatives to reduce its vulnerability to flooding. An operational framework is proposed based on the vulnerability definition of the Intergovernmental Panel on Climate Change (IPCC) and applying a census-based Index of Vulnerability, a geographic information system and local knowledge of urban development. A Principal Component and equal weighting analysis were applied as well as a spatial clustering to explore the spatial vulnerability across the city. A total of 34% of the city area is mapped as having high and very high vulnerability, mostly occupied by informal settlements (e.g., 288 hectares). Underlying factors were poor quality housing, lack of city services and low adaptive capacity of the community. However, some government housing programs (e.g., El Recreo), with better housing and adaptive capacity were also highly vulnerable. Limited urban planning governance has led to the overloading of storm water and drainage infrastructure which cause chronic flooding. Understanding the underlying causes of vulnerability is critical in order develop integrated strategies that increase city resilience to climate change.

Temperate and subtropical sandy beach surf zones present diverse and abundant fauna that are important in local food webs. However, dynamics of these fauna have been poorly studied in tropical areas. The aims of the present study were to describe the small swimming surf-zone fauna (~1–5 mm in length) of two Ecuadorian sandy beaches, determine whether this fauna varies with beach, season or tide, and explore the environmental factors correlated with faunal variability. Beaches were sampled in wet and dry seasons during high, mid- and low tide (2001–2002) by using a hyperbenthic sledge. Beaches were inhabited by an abundant and diverse fauna (>1200 individuals per 100 m2 and >30 taxa), where most individuals were in their early life stages (65%), and the dominant taxa included mysid shrimp (>40% of individuals) and fish and crab larvae (>25 taxa). Composition of groups that are present during their entire life or only early life stages varied most strongly between beaches, potentially because of differences in wave exposure and the influence of an adjacent river, and between seasons with changes in coastal oceanic currents. These results suggest that despite the environmental stability often portrayed for tropical environments, Ecuadorian surf-zone fauna are spatially and temporally variable.

Using data obtained from tide gages in South America, current meters along the equator and the Peru coast, and an array of pressure gages and inverted echo sounders within and around the Galapagos archipelago, we have analyzed the equatorial origin of coastal trapped waves observed by Cornejo‐Rodriquez and Enfield (this issue) along the Peru coast during the intense 1982–1983 El Niño. The propagating fluctuations along the coast were much stronger at that time than either before or after the El Niño, and the variability was not locally forced by coastal winds. We find that the coastal variability was also more energetic during previous El Niño occurrences. At periods of 1–2 weeks the meridional component of currents on the equator is up to an order of magnitude more energetic than the zonal fluctuations and is consistently associated with sea level that fluctuates antisymmetrically between hemispheres. At periods longer than 2 weeks the zonal velocity component is more energetic, and the cross‐equatorial sea level variability is symmetric. The meridional and zonal phase structures of cross spectra involving the currents and sea level establish the 1‐ to 2‐week equatorial fluctuations as mixed Rossby‐gravity (Yanai) waves of low wave number with infinite phase speed (standing oscillations) in the middle of the band (10 days); the corresponding structures for longer periods are consistent with nondispersive Kelvin waves. Frequency domain EOF modes of the sea level and current data establish the mixed Rossby‐gravity waves as the principal source of the strong trapped wave variability in the 1‐ to 2‐week band along the Ecuador‐Peru coast during the 1982–1983 El Niño episode.

Tide and wind data from coastal and island stations from Buenaventura, Colombia (4°N), to Callao, Peru (12°S), have been analyzed for the 1979–1984 time period to determine the propagation and forcing characteristics of coastal sea level variability at periods of days to weeks, as well as how they vary either with season or between the 1982–1983 El Niño‐Southern Oscillation (ENSO) period and non‐ENSO years. During four non‐ENSO years, the ensemble averaged cross spectra between coastal sea level height (SLH) and local winds show weak evidence of local forcing during the whole year without significant differences between the austral summer and winter seasons, other than a greater energy in the wind fluctuations at Talara during summer. Cross spectra between SLH series from neighboring stations show evidence of poleward phase propagation during winter seasons at speeds of about 2.0 m s⁻¹.between La Libertad and Talara at periods of a week or more, and about 2.7 m s⁻¹ between Talara and Callao at periods of 5–11 days, but no propagation is found during summers. During the 1982–1983 ENSO there is a large increase in SLH energy at most frequencies at all coastal stations, but especially in the 8‐to‐11‐day band, where energies are enhanced by as much as an order of magnitude above non‐ENSO levels. The cross spectra between adjacent SLH stations indicate a nondispersive poleward propagation of events during the 1982–1983 ENSO with phase speeds of 2.2–3.5 m s⁻¹ from La Libertad to Talara (periods of a week or more) and 3.4–3.6 m s⁻¹ from Talara to Callao (3.5 days or more). As with the SLH energy, the coherence and phase propagation were much stronger along the Peru coast in 1982–1983 than during non‐ENSO periods, especially in the 8‐to‐11‐day band. The one‐third increase in phase speeds during the ENSO over the non‐ENSO speeds is found to be consistent with the anomalous depression of the density structure during El Niño. Comparisons between coastal SLH and the local alongshore wind suggest that locally forced SLH variability was obscured during the 1982–1983 ENSO by the noncoastally forced, but energetic propagating fluctuations, which probably originated in the equatorial waveguide.