Sediment budget analysis of the Guayas River using a process-based model

Abstract

Abstract. The equatorial Daule and Babahoyo rivers meet and combine into the tidal Guayas River, which flows into the largest estuary on the Pacific coast of South America. The city of Guayaquil, located along the Guayas, is the main port of Ecuador but, at the same time, the planet's fourth most vulnerable city to future flooding due to climate change. Sedimentation, which has increased in recent years, is seen as one of the factors contributing to the risk of flooding. The cause of this sedimentation is the subject of the current research. We used the process-based Delft3D FM model to assess the dominant processes in the river and the effects that past interventions along the river and its estuary have had on the overall sediment budget. Additionally, a simulation including sea level rise was used in order to understand the possible future impact of climate change on the sediment budget. Results indicate an increase in tidal asymmetry due to land reclamation and a decrease in episodic flushing by river floods due to upstream dam construction. These processes have induced an increased import of marine sediment potentially responsible for the observed sedimentation. This is in contrast with the local perception of the problem, which ascribes sedimentation to deforestation in the upper catchment. Only the deposition of silt and clay in connected stagnant water bodies could perhaps be ascribed to upstream deforestation.

Conservation agriculture can help the South American Andean region achieve food security

“…Upstream erosion lowers water quality and leads to siltation and associated flooding downstream (Barrowclough et al, 2016;Barrera Crespo et al, 2019;Restrepo & Escobar, 2018;Rosas et al, 2020). Climate change will not only affect the sustainability of soils in the higher elevations but will also impact lower elevation areas, where siltations will reduce water storage and create greater potential for flooding (Barrera Crespo et al, 2019).…”

“…), so they have to be established off-season (Alwang et al, 2013). Delgado et al (2019) and Barrera et al (2019) found that there was enough moisture for the establishment of an oat (Avena sativa L.)-vetch (Vicia sativa L.) mix planted right after harvest of the cash crop. Alwang et al (2013) found that more than 30% of the cover crops in CA trials could not be established without supplementary water after the cash crop was harvested.…”

Impacts of Climate Change on the Precipitation and Streamflow Regimes in Equatorial Regions: Guayas River Basin

“…The second, the coastal region, is a region of high aggressiveness, with greater erosive potential and sedimentation problems in the lower part of the basin due to the erosive capacity of rainfall [40]. The Guayas River basin has been affected by extreme phenomena such as El Niño [41], which caused flooding in 1965, 1972, 1973, 1976, 1983, 1987, 1992 and 1998 [36,39,42], and La Niña [43]. The lower part of the basin has greater exposure to flooding [44].…”

Compound Effects of Flood Drivers and Wetland Elevation Correction on Coastal Flood Hazard Assessment

“…This package can handle dynamic 10.1029/2020WR027544 interactions of storm surge, hurricanes, and tsunamis and provide detailed information of water level, flow rates, and velocity (Deltares, 2019a). Furthermore, this package has been widely used in similar compound flooding and river discharge-tide interaction studies (Barrera et al, 2019;Kumbier et al, 2018;Muñoz et al, 2020), and salt marsh research (Fagherazzi et al, 2014;Marciano et al, 2005) including intertidal creeks and overmarsh circulation analyses in Savannah's wetlands with satisfactory results (Sullivan et al, 2015(Sullivan et al, , 2019.…”

“…Bottom friction coefficients associated with the Atlantic Ocean and river bed are calibrated recursively in order to replicate the observed total water levels from USGS and NOAA stations with high accuracy. We use spatially varying bed roughness values in the Savannah model to account for anthropogenic interventions (e.g., dredged river channel, Figure 2b), heterogeneities in river morphology, and sediment deposition patterns within fluvial to tidal transition zones (Barrera et al, 2019;Hoitink et al, 2017;Kästner et al, 2017). The calibrated Manning's coefficient values in the model domain are n = 0.018 (Atlantic Ocean), n = 0.042 (dredged channel), and n = 0.035 (upstream part or the river).…”