Riverbank failures are becoming an increasingly important infrastructure challenge as climate variability intensifies flooding and rapid changes in river water levels. Across many parts of Indonesia, unstable riverbanks threaten roads, residential areas, irrigation systems, and public facilities. Bojonegoro is particularly vulnerable because seasonal fluctuations in river discharge frequently alter the pressure exerted on riverbanks, increasing the likelihood of slope failure.
According to Wahyu Nursamhuda and Hendrik Richard of Cipta Wacana Christian University, the riverbank at Ledok Kulon Village had already reached a critical condition before reinforcement was considered. Preliminary assessments found that most slope sections failed to meet Indonesia's minimum geotechnical safety requirement, indicating that structural intervention was urgently needed to prevent future landslides.
Field Investigation Combined with Digital Engineering
Rather than relying solely on theoretical calculations, the researchers carried out a comprehensive site investigation. Soil samples were collected through boreholes and field testing to determine the engineering characteristics of the riverbank. The information was then incorporated into GEO5, a geotechnical engineering software package that simulated how the riverbank would respond under different environmental conditions.
The research evaluated three realistic scenarios:
- Normal river conditions (C1)
- Flood conditions (C2)
- Rapid drawdown (C3), when river water recedes quickly after flooding
Rapid drawdown is considered one of the most dangerous situations because the supporting pressure from river water disappears faster than excess water pressure inside the soil can dissipate. As a result, the soil temporarily loses strength and becomes much more susceptible to collapse.
Existing Riverbanks Were Already Unsafe
The numerical analysis revealed that the existing slopes were already unstable before reinforcement.
Nearly every riverbank section recorded a Factor of Safety (FoS) below the required minimum value of 1.50. The most critical location was Section P3, where resisting forces were insufficient to balance overturning forces, clearly indicating an elevated risk of slope failure.
These findings explain why conventional erosion control measures alone would not adequately protect the site. Instead, the researchers proposed an integrated reinforcement system capable of addressing both erosion and deep-seated slope instability.
Integrated Protection System Performs Better
The proposed protection system combines three structural components:
- Gabion walls to protect the riverbank surface from erosion.
- Flat Concrete Sheet Piles (FCSPs) to resist lateral soil movement.
- Mini-pile foundations to strengthen the structural support beneath the retaining system.
Together, these elements were designed to function as a unified riverbank stabilization system rather than independent structures.
Simulation results showed that gabion walls alone performed well during normal river conditions, exceeding the required safety standards against overturning, sliding, and foundation failure. However, their performance declined substantially during flood events and especially during rapid drawdown, highlighting the need for additional reinforcement.
Rapid Drawdown Is the Greatest Threat
Among all loading conditions, rapid drawdown (C3) emerged as the most critical.
Under this scenario, one analyzed section recorded a safety factor against overturning of only 0.54, while resistance against sliding dropped to 0.26, well below acceptable engineering limits. The researchers attributed this instability to the site's extremely low soil permeability, which delayed the release of pore water pressure after river levels fell rapidly.
This finding reinforces the importance of considering sudden water-level changes—not only flooding itself—when designing riverbank protection systems.
FCSP Reinforcement Demonstrated Strong Structural Capacity
While gabion walls alone proved insufficient under the most severe conditions, the integrated design incorporating Flat Concrete Sheet Piles (FCSPs) delivered considerably stronger performance.
The numerical analysis predicted:
- Maximum bending moment: 26.95 kN·m/m
- Maximum shear force: 22.06 kN/m
- Maximum structural displacement: 14.6 mm
- Factor of Safety against passive earth pressure failure: 9.18, substantially higher than the required minimum of 1.50.
Practical Benefits Beyond Bojonegoro
The study has implications that extend beyond a single village.
Many Indonesian river systems experience seasonal flooding followed by rapid declines in water levels. Similar soil conditions are also common in many lowland areas. Consequently, the integrated protection strategy proposed by Wahyu Nursamhuda and Hendrik Richard could serve as a practical engineering reference for local governments, infrastructure planners, consultants, and contractors responsible for riverbank stabilization projects.
The research also supports evidence-based infrastructure planning by demonstrating how numerical simulations and field investigations can reduce engineering uncertainty before construction begins.
As Wahyu Nursamhuda and Hendrik Richard of Cipta Wacana Christian University conclude, the integrated combination of gabion walls, mini-pile foundations, and Flat Concrete Sheet Piles provides a technically reliable solution capable of satisfying Indonesia's geotechnical design standards while significantly improving riverbank stability under challenging hydraulic conditions.
Author Profile
Wahyu Nursamhuda is a researcher from Cipta Wacana Christian University specializing in geotechnical engineering, slope stability, and riverbank protection systems.
Hendrik Richard is a lecturer and researcher at Cipta Wacana Christian University whose expertise includes civil engineering, structural engineering, and geotechnical design, particularly numerical analysis for infrastructure safety. (Fields of expertise are inferred from the published research topic.)
Source
Article Title: Design and Planning of Riverbank Protection in Ledok Kulon Village, Bojonegoro
Authors: Wahyu Nursamhuda; Hendrik Richard
Affiliation: Cipta Wacana Christian University
Journal: International Journal of Sustainable Applied Sciences (IJSAS)
Publication Year: 2026
DOI: https://doi.org/10.59890/ijsas.v4i7.21
Official Journal: http://ijsasjournal.my.id/index.php/ijsas
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