Project Name: Zarumilla Riverbank Stabilization
Project Location: Tumbes and Zarumilla Rivers in Peru
Rivers and streams are dynamic waterways shaped by the sediments and water they carry. While we may think of rivers as stable features of the landscape, their constantly changing nature can significantly affect the surrounding land. Riverbank erosion is one such change that can lead to unfavorable outcomes that can reach far beyond the area where the erosion is occurring. Communities down the river can be adversely affected by erosion as it sends extra sediment downstream, changing the river’s course, altering fish and game habitats, and impacting navigation conditions in shipping channels, ports, and harbors.
The Problem: Riverbank Erosion Affects Tumbes Area
The Zarumilla River, which marks the border between Peru and Ecuador, is part of the Gulf of Guayaquil-Tumbes mangroves. The river’s currents, sediments, and tides strongly influence the geomorphology of this area. A portion of the riverbank located in the remote Tumbes region in Northwestern Peru was experiencing severe erosion. This particularly vulnerable area required a riverbank protection solution to prevent further deterioration of the riverbank.
The extreme El Niño event caused the western Pacific to warm, developing atmospheric convection and increased rainfall. The storm events caused catastrophic flooding and severe erosion in the eastern equatorial region of Ecuador and Northern Peru. The outcome of these storms, combined with the implications of climate change, necessitated the implementation of a resilient and cost-effective solution to adapt this important waterway to withstand extreme weather events, particularly as these types of events are expected to increase in frequency and intensity in the future.
The Solution: Hard-Armored Shoreline Protection System Stabilizes Riverbank Slope & Prevents Erosion
The GEOWEB® Shoreline Protection System with concrete infill was selected to protect the Zarumilla riverbank against future storm events. The GEOWEB system with concrete infill provides economical, hard-armored protection of slopes and channels exposed to high flow velocities and high shear stresses. The system has been proven to withstand sustained flow velocities over 36 ft/s (11 m/s) and shear stresses of 20.9 psf (1.0 kPa), outperforming rip-rap, gabions, and other conventional hard armor strategies.
The quality, surface finish, and thickness of the concrete can be selected to meet specific design needs. The concrete-filled GEOWEB system comprises flexible, poured-in-place sections that are more economical than articulated concrete block systems (ACBs) and do not require specialized equipment to install.
The system also provides excellent resistance to sheet flow, preventing the formation of rills and gullies—especially in areas of concentrated flow over erosive soils. In many cases, protection of the slope surface may also allow for the construction of steeper embankments, with less horizontal footprint, thereby conserving valuable land space.
Contractors installed 222,998 square meters of the GEOWEB system along the compromised riverbank slope. Installation rates are typically around 120 square meters per hour for a crew of four. At the Zarumilla project, the contractor further optimized installation rates by pre-staging sections and assembling the system on the crest before expanding the panels down the slope face.
The GEOWEB Shoreline Protection System is quick and easy to install and does not require specialized equipment or training. The complete system is formless and poured in place, eliminating the need for conventional concrete formwork and rebar reinforcement while ensuring consistent pour depths (thereby optimizing material volumes and minimizing the likelihood of over-pouring).
The product was shipped to the site in September 2020, and installation was complete by December 2020. The project was completed on schedule and within budget. The GEOWEB® Shoreline Protection System is performing to expectations and will provide much-needed protection to the Zarumilla River, and the communities that depend on it when the next major storm hits.
Benefits of Concrete-Filled GEOWEB 3D Confinement System
- The formless system reduces construction costs by eliminating conventional forms and reinforcement. Installation is fast, efficient, and flexible.
- The selected cell depth ensures uniform concrete depth, controls concrete quantities and costs and allows the use of an easier-to-install, higher slump concrete.
- The system becomes a flexible concrete slab that conforms to minor subgrade movement, prevents uncontrolled cracking, and reduces the potential of piping or undermining.
- The system can accommodate higher permissible shear stresses than erosion control blankets, turf reinforcing mats, rip-rap, and gabions.