Water Hyacinth Geotextiles as a Nature-Based Solution for Riverbank Protection in the Vietnamese Mekong Delta

Abstract

Riverbank erosion in the Vietnamese Mekong Delta (VMD) poses a serious threat to agricultural lands, infrastructure, and local communities. Conventional protective measures, such as synthetic geotextiles and concrete revetments, are often costly and environmentally disruptive. This study investigates the potential of Eichhornia crassipes, a widely available invasive species, commonly known as water hyacinth (WH), to produce biodegradable geotextiles as a low-cost, nature-based solution (NbS) for small-scale riverbank protection. It is the first to test minimally processed WH mats under simulated tidal conditions in the VMD. Laboratory experiments were conducted to evaluate the geotextile’s (1) sediment retention capacity, (2) wave energy reduction, and (3) mechanical durability under wet–dry cycles. Results show that the WH geotextile effectively reduced sediment resuspension, decreasing turbidity levels from 800 FTU (unprotected scenario) to below 50 FTU. The geotextile also attenuated wave energy, reducing significant wave heights by approximately 35–40%. Mechanical testing revealed that the fish bone weaving pattern with adhesive coating achieved the highest tensile strength (8.36 kN/m after 12 wet–dry cycles), while uncoated samples demonstrated higher elongation (up to 61.67%), providing greater flexibility. These demonstrate the feasibility of WH geotextiles as a scalable nature-based solution for erosion-prone tropical deltas. Future studies should focus on field-scale validation, biodegradation rates, and performance optimization for long-term applications.

1. Introduction

Riverbank erosion in the Vietnamese Mekong Delta (VMD) is driven by complex hydrodynamic forces, including tidal fluctuations, sediment deficits, and human-induced pressures. These dynamics threaten agricultural productivity, infrastructure, and the safety of over 17 million inhabitants [1,2,3,4]. Conventional engineering solutions such as concrete revetments or synthetic geotextiles, while effective, are costly and may have negative environmental impacts [5]. In recent years, nature-based Solutions (NbS) have emerged as promising alternatives that leverage local materials and ecological processes to enhance climate resilience in riverine and deltaic landscapes [6].

Systematic approaches to reviewing emerging materials (e.g., in construction technologies) demonstrate how structured evidence synthesis can strengthen research positioning [7]. While our study is experimental in scope, we draw on these insights to situate WH (Eichhornia crassipes) geotextiles within broader NbS discussions.

WH is a fast-growing invasive aquatic plant, and is abundant in the VMD. Its rapid proliferation causes environmental issues such as reduced water quality, impaired navigation, and ecosystem imbalances [8]. Notably, the plant’s high cellulose and hemicellulose content makes it a promising raw material for developing biodegradable geotextiles, offering a circular solution to an ecological nuisance. [9]. Several studies have evaluated WH and other natural fibers for soil stabilization and erosion control, noting both their environmental benefits and limitations in tensile strength and durability [10,11,12]. For example, Tanchaisawat et al. [10] and Artidteang et al. [11] demonstrated the feasibility of WH geotextiles for soil stabilization. However, their low tensile strength and limited durability, particularly under repeated wetting and drying cycles, remain critical challenges [9,13]. By comparison, jute and coir mats offer high tensile strength and slower degradation [6,10], while bamboo geotextiles withstand strong hydraulic loads but lack flexibility. WH remains less studied, mainly in soil stabilization and composites [12,13].

Recent research has shown that coating water hyacinth-based geotextiles with natural rubber can significantly enhance their durability and tensile strength, making them suitable for erosion control in tropical climates [14]. Despite these advances, no study has examined the direct application of untreated or minimally processed WH geotextiles for small-scale riverbank protection in the VMD. There is also a broader debate on the long-term reliability of biodegradable geotextiles in dynamic environments: some studies suggest that rapid biodegradation can compromise structural integrity [15], while others argue that their temporary nature facilitates vegetation growth and long-term stabilization [6,15]. However, no prior study has systematically assessed the use of minimally processed WH fibers for biodegradable geotextiles tailored to small-scale riverbank protection in the VMD context.

WH is one of the world’s most invasive aquatic species, with high biomass productivity and rapid proliferation in tropical freshwater systems [16]. In the VMD, it contributes to ecosystem degradation and navigation problems. However, its fibrous structure and high cellulose content make it a promising raw material for bio-based products. Utilizing WH in erosion control applications presents an opportunity to repurpose waste biomass into functional materials—advancing both NbS and circular economy principles.

This study addresses these gaps by investigating the use of WH to produce geotextiles as a low-cost, environmentally friendly NbS for small riverbank protection in the VMD. The research focuses on (1) evaluating the sediment retention capacity of the geotextile, (2) analyzing its wave absorption performance, and (3) assessing its mechanical durability under wet–dry cycles caused by tidal fluctuations. Laboratory results show that the geotextile effectively sustains sediment along the riverbank, exhibits a notable ability to absorb incident wave energy, and maintains a tensile strength of approximately 5 kN/m after multiple wet–dry cycles, despite an initial reduction. These findings highlight the potential of water hyacinth-based geotextiles as a sustainable solution for mitigating riverbank erosion in the VMD.

2. Materials and Methods

2.1. Measuring the Sediment Retention Capacity of the Geotextile

2.1.1. Preparation of WH Geotextile

WH was collected from a local river in the VMD. After harvesting, the plants were cleaned thoroughly to remove any dirt and organic debris, then left to dry naturally under the sun for approximately 3 to 5 days until the moisture content was reduced to an appropriate level. Once dried, the stalks were manually woven using a traditional hand-weaving technique to form geotextile mats. Each mat was approximately 58 × 29 × 01 cm (1682 cm²) (Figure 1). The geotextiles were then trimmed to match the dimensions of the experimental soil bed in the wave flume.

2.1.2. Experimental Setup and Procedure

Figure 2 shows the experimental setup in the wave flume. Figure 2a provides an overall view of the wave flume used in the laboratory experiments. The wave paddle and its driving engine are shown in Figure 2b, responsible for generating consistent wave conditions. Figure 2c indicates the placement of the Levelogger sensor, which records water level fluctuations for wave height analysis. Figure 2d illustrates the test section where the WH geotextile was installed. The Infinity turbidity sensor was positioned immediately in front of the geotextile to measure the turbidity induced by sediment erosion. A soil sample, representing the riverbank, was placed within a steel box inclined at an angle to simulate a natural riverbank slope.

The experimental investigation was carried out in a wave flume designed to replicate riverbank conditions subjected to wave action. The soil sample was placed on a bed inclined at a 1:2.5 (horizontal to vertical) slope to simulate a natural riverbank. Two sensors were installed in the flume: a Levelogger, which was used to record water level fluctuations throughout the experiments, and an Infinity turbidity meter, which measured changes in water turbidity as an indicator of sediment loss.

Two tests were conducted to assess the geotextile’s effectiveness: (1) a control test exposing a bare soil slope to wave action, and (2) a treatment test with the slope protected by the WH geotextile mat. Both tests were performed under identical wave conditions for a continuous duration of 48 h. Waves were generated using a programmable paddle installed at the upstream end of the flume, and wave parameters such as height and period were kept constant to ensure consistency between the two scenarios. Sediment loss was monitored through changes in turbidity, and visual observations were made to assess soil surface stability during and after each test.

2.2. Calculating Significant Wave Height for Assessing Wave Height Reduction

In this study, the significant wave height (H_s) was used to evaluate the effectiveness of wave height reduction in the WH geotextile. The significant wave height is a statistical parameter that represents the average height of the highest one-third of waves in a wave record. If N individual wave heights (H_i) are ordered from largest to smallest, then H_s can be defined as

$$H_s={\displaystyle \frac{1}{N/3}}{\displaystyle \sum _{i=1}^{N/3}{H}_i}$$

(1)

In this study, water level time series were collected using a Levelogger pressure sensor. Since the measured dataset consists of surface elevation fluctuations over time, the sigma method was employed to estimate the significant wave height. This method is appropriate for pressure-derived wave data as it directly relates wave energy to the variance of the water surface elevation. The significant wave height was calculated using the following equation [17,18]:

H_s = 4 × σ_η

(2)

where σ_η is the standard deviation of the water surface elevation η within a specified time. The sigma method was selected for its compatibility with pressure-derived surface elevation data and its reliability in estimating wave energy variability.

2.3. Testing the Mechanical Durability Under Wet–Dry Cycles Due to Tidal Fluctuations

The mechanical durability test of the water hyacinth geotextile under wet–dry cycles caused by tidal fluctuations was conducted in two steps. The first step involved the preparation of test samples, and the second step consisted of testing the tensile strength of the geotextile using an Instron tensile testing machine (Figure 3).

2.3.1. Preparing the Test Sample

Two types of geotextiles were used in the test, both produced from WH but differing in their weaving methods. The first type is referred to as the “custard apple seed” pattern (Figure 4a), while the second type is called the “fish bone” pattern (Figure 4b). These names are English translations of the original Vietnamese weaving terms.

For each weaving method, two variations in geotextiles were prepared:

• With Callux® CL 326 adhesive coating.
• Without Callux® CL 326 adhesive coating.

Each wet–dry cycle involved 6 h of submersion followed by 6 h of air-drying, repeated continuously over 6 days for a total of 12 cycles. Four samples were collected at every second cycle for mechanical testing, resulting in a total of 24 geotextile samples as summarized in

Table 1. Wet–dry cycle test process.

No	Date	Time	Status	Notes
1	5 July 2025	05:00	Wet	Submerge 24 geotextile samples in water
2		11:00	Dry	Remove 24 geotextile samples from water
3		17:00	Wet	Submerge 24 geotextile samples in water
4		23:00	Dry	Remove 24 geotextile samples from water
5	6 July 2025	05:00	Wet	Submerge 20 geotextile samples in water; collect 4 samples (2 cycles)
6		11:00	Dry	Remove 20 geotextile samples from water
7		17:00	Wet	Submerge 20 geotextile samples in water
8		23:00	Dry	Remove 20 geotextile samples from water
9	7 July 2025	05:00	Wet	Submerge 16 geotextile samples in water; collect 4 samples (4 cycles)
10		11:00	Dry	Remove 16 geotextile samples from water
11		17:00	Wet	Submerge 16 geotextile samples in water
12		23:00	Dry	Remove 16 geotextile samples from water
13	8 July 2025	05:00	Wet	Submerge 12 geotextile samples in water; collect 4 samples (6 cycles)
14		11:00	Dry	Remove 12 geotextile samples from water
15		17:00	Wet	Submerge 12 geotextile samples in water
16		23:00	Dry	Remove 12 geotextile samples from water
17	9 July 2025	05:00	Wet	Submerge 8 geotextile samples in water; collect 4 samples (8 cycles)
18		11:00	Dry	Remove 8 geotextile samples from water
19		17:00	Wet	Submerge 8 geotextile samples in water
20		23:00	Dry	Remove 8 geotextile samples from water
21	10 July 2025	05:00	Wet	Submerge 4 geotextile samples in water; collect 4 samples (10 cycles)
22		11:00	Dry	Remove 4 geotextile samples from water
23		17:00	Wet	Submerge 4 geotextile samples in water
24		23:00	Dry	Remove 4 geotextile samples from water (12 cycles)

.

2.3.2. Tensile Strength Testing

After the wet–dry cycle preparation, the geotextile samples were transported to the Environment and Construction Experimental Center of Mien Tay Construction University for tensile strength testing.

Since the original geotextile sheets had dimensions of 58 × 29 cm, they were cut into smaller samples of 20 × 20 cm, as required by the Instron tensile testing machine.

The tensile tests were conducted in accordance with the Vietnamese standard TCVN 8871-1÷6:2011: Geotextiles—Parts 1–6: Standard Test Methods [19]. Each sample was fixed in the machine grips and stretched at a constant rate until failure, with both maximum tensile load (kN/m) and elongation at break (%) being recorded. For geotextile testing according to TCVN 8871-1÷6:2011 [19], the tensile strength is often expressed in terms of tensile force per unit width:

$$N={\displaystyle \frac{F_{\max }}{w}}$$

(3)

where N is tensile strength per unit width (kN/m), F_max is maximum load at failure (N) and w is the width of the test specimen (m).

The elongation at maximum tensile load (ε, %) was calculated as the ratio of the increase in specimen length at failure (ΔL, m) to the original gauge length (L₀, m), expressed as a percentage:

$$\epsilon (\%)={\displaystyle \frac{\Delta L}{L_0}}\times 100$$

(4)

3. Results

3.1. Sediment Retention

Figure 5 illustrates turbidity levels over 48 h for the unprotected and WH-protected soil slopes under identical wave conditions. In the unprotected scenario, turbidity rapidly increased from near-zero to approximately 800 FTU within the first five hours and remained elevated throughout the test, indicating continuous sediment resuspension due to wave action.

In contrast, the WH geotextile significantly reduced sediment loss. While an initial peak of approximately 600 FTU was observed, turbidity quickly declined and stabilized around 50 FTU for the remainder of the experiment. This 90–95% reduction in turbidity highlights the geotextile’s effectiveness in minimizing soil disturbance and retaining fine sediments along the riverbank slope. In contrast, turbidity in the unprotected scenario increased rapidly from near zero at the beginning of the test to about 800 FTU within the first 5 h. This high level of turbidity was sustained throughout the remainder of the experiment, indicating continuous sediment disturbance and transport in the absence of geotextile protection.

These results clearly demonstrate the potential of the WH geotextile as a nature-based solution for riverbank protection by mitigating wave-induced erosion and retaining soil materials.

3.2. Wave Energy Reduction

Figure 6 presents the time series of significant wave heights (H_s) for both text conditions. Although the wave maker was operated at a constant setting to generate uniform wave energy across both tests, notable differences in H_s values are observed between the two cases.

In the test without the WH mat, the wave heights remained consistently higher throughout the experiment. In contrast, the test with the WH mat exhibited lower Hs values at most time intervals, indicating the damping effect of the geotextile layer on wave energy. This discrepancy suggests that the presence of the WH mat contributed to wave energy dissipation, likely by absorbing and scattering wave forces at the interface.

Additionally, the differences in turbidity between the two tests may have influenced wave dynamics. Higher turbidity levels, observed in the unprotected scenario, can be associated with increased sediment suspension and resuspension, which may alter near-bed flow conditions and reflect in the wave height signal.

3.3. Mechanical Durability Under Wet–Dry Cycles

3.3.1. Maximum Tensile Strength of the Geotextiles

Table 2. Maximum tensile strength N (kN/m) of WH geotextiles with different weaving patterns and adhesive coating conditions under multiple wet–dry cycles.

Days	Wet–Dry Cycles	Maximum Tensile Strength—N (kN/m)
		Without Adhesive Coating		With Adhesive Coating
		Custard Apple Seed	Fish Bone	Custard Apple Seed	Fish Bone
1	2	10.44	13.65	14.21	21.89
2	4	3.8	4.95	5.82	3.86
3	6	6.9	6.06	3.61	2.09
4	8	4.02	5.65	5.62	6.15
5	10	2.26	4.38	5.43	7.61
6	12	5.66	5.82	5.53	8.36

and Figure 7 present the variation in the maximum tensile strength (N) of the WH geotextile after every 2 wet–dry cycles, considering both weaving methods (custard apple seed and fish bone) and the presence or absence of adhesive coating.

Regarding the effect of Adhesive Coating (Figure 7a,b), the geotextiles with adhesive coating generally exhibit higher tensile strengths compared to those without coating. For the custard apple seed pattern, the tensile strength decreases sharply from 14.21 kN/m (2 cycles) to 5.82 kN/m (4 cycles), before stabilizing around 5.5 kN/m after 10–12 cycles. Similarly, the fish bone pattern with adhesive coating shows a significant initial drop from 21.89 kN/m (2 cycles) to 3.86 kN/m (4 cycles), but then gradually recovers and stabilizes around 8.36 kN/m after 12 cycles. This indicates that the adhesive layer improves long-term durability by maintaining a higher residual strength despite early losses.

Concerning the effect of Weaving Pattern (Figure 7c,d), comparisons between weaving patterns reveal that the fish bone pattern consistently demonstrates higher tensile strength than the custard apple seed pattern under the same coating condition. For uncoated geotextiles, the fish bone pattern retains 5.82 kN/m after 12 cycles, compared to 5.66 kN/m for the custard apple seed pattern. With adhesive coating, the fish bone pattern not only starts with a much higher tensile strength (21.89 kN/m) but also maintains 8.36 kN/m after 12 cycles, nearly 50% higher than the custard apple seed pattern.

Both weaving patterns show a noticeable decrease in tensile strength during the first four wet–dry cycles, primarily due to fiber swelling, loosening, and structural changes caused by repeated moisture absorption and drying. However, after approximately six cycles, the tensile strength begins to stabilize, indicating that the geotextiles have reached a balanced mechanical state. This stabilization suggests that the materials are capable of maintaining sufficient strength for long-term field applications, even under fluctuating wet and dry conditions.

Overall, the fish bone geotextile with adhesive coating demonstrates the best mechanical durability, maintaining a tensile strength of 8.36 kN/m after 12 wet–dry cycles, which is significantly higher than all other configurations. The custard apple seed pattern, while less robust, still retains adequate strength (>5 kN/m) for small-scale riverbank protection. These results highlight that both weaving pattern and adhesive coating play critical roles in improving the long-term performance of WH geotextiles under alternating wet and dry conditions.

3.3.2. Elongation of the Geotextiles at Maximum Tensile Strength

Table 3. Elongation at N_max (%) of WH geotextiles with different weaving patterns and adhesive coating conditions under multiple wet–dry cycles.

Days	Wet–Dry Cycles	Elongation at Nmax (%)
		Without Adhesive Coating		With Adhesive Coating
		Custard Apple Seed	Fish Bone	Custard Apple Seed	Fish Bone
1	2	16.67	16.34	13.1	18.1
2	4	21.67	23.34	48.34	28.34
3	6	21.67	21.67	22.67	32.01
4	8	30.1	61.67	11.01	25.34
5	10	36.67	30.67	32.67	25.67
6	12	24.67	24.67	27.67	24.67

and Figure 8 present the elongation at maximum tensile strength (N_max) of WH geotextiles subjected to multiple wet–dry cycles, considering both weaving patterns (custard apple seed and fish bone) with and without adhesive coating. The data reveal clear differences in elongation behavior depending on the weaving pattern and coating condition.

For geotextiles without adhesive coating, the elongation at N_max generally ranges between 16–62%. The fish bone pattern shows greater elongation capacity, reaching a maximum of 61.67% after 8 cycles, while the custard apple seed pattern achieves a more moderate increase, peaking at 36.67% after 10 cycles. In contrast, coated geotextiles exhibit lower elongation values, varying between 11–48%. The custard apple seed pattern demonstrates a notable peak elongation of 48.34% at 4 cycles, whereas the fish bone pattern peaks at 32.01% at 6 cycles. These results indicate that adhesive coating reduces fiber flexibility, leading to lower elongation values compared to uncoated samples.

Figure 8a,b further illustrate these trends. Figure 8a, which compares uncoated geotextiles, shows that the fish bone pattern undergoes significant variation, with a sharp increase up to 61.67% at 8 cycles, while the custard apple seed pattern increases steadily to 36.67% at 10 cycles. Figure 8b, representing coated geotextiles, highlights that adhesive coating constrains fiber movement and results in overall lower elongation, yet the coated custard apple seed geotextile achieves higher elongation peaks than the coated fish bone pattern during the initial cycles.

In general, the absence of coating provides higher elongation due to increased fiber mobility, while adhesive coating offers structural rigidity, which lowers elongation but improves tensile strength (as seen in Section 3.3.1). Among the weaving patterns, fish bone exhibits superior elongation in uncoated form, whereas custard apple seed performs better under coated conditions. Overall, the observed elongation range of 10–60% suggests that these geotextiles maintain sufficient flexibility to accommodate deformation before failure, which is advantageous for field applications where adaptability to environmental stresses is required.

4. Discussion

The results of this study demonstrate the potential of WH geotextiles as a low-cost, biodegradable material for riverbank protection in the VMD. The laboratory experiments confirmed the geotextile’s effectiveness in reducing sediment resuspension and attenuating wave energy, while maintaining mechanical integrity under repeated wet–dry cycles—conditions typical of tidal riverbanks.

The significant turbidity reduction observed (from 800 FTU to ~50 FTU) aligns with earlier findings by Tanchaisawat et al. [10] and Artidteang et al. [11], who reported that WH-based geosynthetics can provide sufficient soil stabilization and erosion control when applied under controlled conditions. In this study, turbidity decreased sharply after initial wave-induced disturbance and remained low, suggesting that the mat not only limits sediment displacement but also stabilizes the soil–water interface. This sediment retention function is critical in deltaic environments, where fine-grained soils are highly susceptible to erosion.

Beyond short-term sediment trapping, filtration performance depends on the geotextile’s ability to balance soil retention with adequate permeability. A key risk in long-term applications is clogging or blinding, whereby fine sediments accumulate in the geotextile pores and reduce hydraulic conductivity. Studies on synthetic geotextiles have shown that clogging can significantly impair drainage and filtration capacity over time, particularly in fine-grained soils [5,20]. Research on biodegradable mats, including coir and jute, similarly notes a decline in permeability with prolonged sediment deposition, though vegetation growth may partially offset this by reinforcing soil and restoring porosity [6]. For WH mats, the high fiber porosity observed in laboratory conditions suggests initial permeability is sufficient, but their long-term filtration behavior under sustained sediment loads remains unknown. This highlights the need for field-scale monitoring of clogging potential and permeability changes to ensure reliable hydraulic function alongside erosion control.

Similarly, the observed 35–40% reduction in significant wave height confirms the energy dissipation function of WH mats. Their fibrous structure and surface roughness likely contributed to the scattering and absorption of wave energy, an effect previously reported in studies on natural fiber geotextile [6,13]. These findings suggest that WH geotextiles can effectively mitigate wave-induced erosion processes, especially in small riverbank settings where conventional hard structures may be economically or environmentally unsuitable.

The mechanical testing further demonstrated the durability of the geotextile under simulated tidal conditions. Tensile strength stabilized after six wet–dry cycles, indicating that the fibers reached a mechanical equilibrium, possibly due to compaction and realignment during repeated moisture fluctuations. The fish bone weave, particularly with adhesive coating, consistently outperformed other configurations—maintaining over 8 kN/m of tensile strength after 12 cycles. This durability compares favorably to other natural-fiber geotextiles and meets typical engineering thresholds for small-scale erosion control applications [13,14].

The observed trade-off between tensile strength and elongation provides important design insights. Uncoated mats exhibited greater flexibility (elongation up to 61.67%), allowing them to conform to irregular riverbank surfaces and accommodate soil settlement or vegetation growth without tearing. Coated mats, by contrast, showed reduced elongation but higher structural rigidity and resistance to tensile failure, which may be advantageous under strong hydraulic forces or wave attack. In dynamic field environments, this balance suggests that uncoated mats may be more suitable for low-energy, vegetated banks where adaptability is critical, whereas coated mats are better suited for exposed sites requiring greater resistance. Field-based comparisons across diverse hydrodynamic and ecological settings would help refine these application strategies and confirm their long-term effectiveness.

Comparisons with other natural-fiber geotextiles provide useful context for evaluating the performance of WH mats. Jute and coir geotextiles, for example, are widely used for erosion control due to their relatively high tensile strength and slower biodegradation rates; however, they are often imported in the Vietnamese context, increasing costs and limiting local accessibility. Bamboo mats and coir nets have also been shown to withstand hydraulic forces in tropical environments, but their rigid structures can reduce flexibility during installation on irregular slopes. By contrast, WH geotextiles exhibit moderate tensile strength and higher elongation capacity, allowing for better adaptation to uneven terrain, while simultaneously valorizing an invasive species that is abundant in the VMD. This dual ecological and economic advantage differentiates WH mats from other bio-based options, particularly for small-scale, community-based riverbank protection projects where affordability and local resource availability are critical.

In addition, some on-site and large-scale investigations also give useful comparisons. Tanchaisawat et al. (2014) [10] and Artidteang et al. (2015) [11] tested WH-based geosynthetics combined with grasses in real erosion control and they also reported good sediment retention but weak durability under natural wet–dry cycles. Our result that the fish bone with adhesive coating still keeps 8.36 kN/m after 12 cycles is in line with Prongmanee et al. (2023) [13] who improved WH mats with natural rubber for tropical conditions. This shows that the mechanical performance from our lab can connect with field requirements in tropical riverbanks. At the same time, our idea of using WH mats as a proactive and low-cost measure is consistent with Hussain et al. (2023) [21] who reviewed hazard management in Pakistan and found that most strategies focus on post-disaster relief instead of pre-disaster mitigation. From this point, WH geotextile can be seen not only as a material test but also as part of a wider approach to support risk reduction and sustainable riverbank protection.

While the laboratory experiments provide controlled insights into sediment retention, wave attenuation, and mechanical durability, they cannot fully replicate the complexity of field conditions. In natural settings, additional processes such as plant colonization and root reinforcement, seasonal variability in hydrodynamics, and sediment consolidation are likely to influence geotextile performance. Long-term durability is also uncertain, as biodegradation rates may accelerate under prolonged inundation, high microbial activity, or elevated temperatures typical of the VMD. Furthermore, extreme events such as storm surges or sustained flooding could impose hydraulic stresses beyond those simulated in the wave flume. These factors highlight the need for systematic field trials and long-term monitoring to validate laboratory findings, refine design parameters, and ensure that water hyacinth geotextiles provide reliable protection under real-world conditions.

From a broader perspective, the findings of this study contribute to the growing body of evidence supporting NbS for riverbank protection [6]. By utilizing WH, an invasive aquatic plant, this approach not only mitigates erosion but also offers a sustainable method for managing a problematic species in the VMD. The dual benefits of environmental management and riverbank stabilization underscore the practical value of this solution. In line with the IUCN Global Standard on NbS [22,23], the use of WH geotextiles presents a scalable, context-specific solution that delivers multiple co-benefits—erosion control, invasive species management, and sustainable material use. As Seddon et al. (2021) [24] emphasize, successful NbS must be multifunctional, context-appropriate, and socially inclusive, criteria which WH geotextiles begin to meet by combining erosion control, invasive species valorization, and community-scalable fabrication.

These findings also align with Vietnam’s strategic orientation toward nature-based and community-based adaptation under its National Adaptation Plan (NAP) and the Mekong Delta Regional Master Plan (2021–2030). WH geotextiles represent a locally adapted material that could be integrated into sediment management, embankment reinforcement, or rural infrastructure guidelines issued by MONRE and MARD. Their modularity and cost-effectiveness make them especially suitable for decentralized, village-scale interventions that support national climate resilience goals.

Despite the promising laboratory results, this study has several limitations. Experiments were conducted under controlled conditions that do not fully replicate the complexity of field environments, such as interactions with vegetation, sediment consolidation processes, and biodegradation dynamics. Moreover, the geotextile’s performance under extreme hydrological events (e.g., storm surges or prolonged inundation) remains untested. The adhesive used in coated mats, while effective in enhancing durability, also requires further evaluation regarding its biodegradability and environmental compatibility in aquatic ecosystems.

The biodegradation behavior of WH geotextiles is also a critical factor for long-term functionality. While wet–dry cycle tests indicate that mats retain sufficient strength in the short term, in natural conditions microbial activity, enzymatic breakdown of cellulose, and hydrolysis under fluctuating hydrology can accelerate fiber degradation. Recent studies report that bio-based geotextiles often lose significant tensile strength within 6–18 months depending on climate, soil microbiota, and waterlogging intensity [25,26]. This can limit their durability where prolonged protection is required, but it also supports ecological restoration by enabling vegetation establishment and gradual replacement of the mats by root systems. For WH mats, this suggests a role as transitional protective layers—stabilizing banks in the short to medium term until vegetation colonizes. Field-based monitoring of biodegradation rates and vegetation dynamics will therefore be essential to optimize their application in sustainable erosion control.

Beyond their technical functionality, WH geotextiles reflect core principles of the circular economy by converting invasive biomass into a productive material, thereby reducing reliance on synthetic geosynthetics. This valorization pathway transforms an ecological nuisance into a climate adaptation asset, contributing to resource efficiency, waste minimization, and localized material loops. Such approaches align with broader sustainability transitions in deltaic regions that seek to balance ecological restoration with infrastructure resilience. Beyond erosion control, the fabrication and application of WH geotextiles could support rural livelihoods through labor-intensive production models, aligning with employment and sustainable development priorities. Their low-carbon footprint and use of invasive biomass also complement climate mitigation and biodiversity management objectives, offering a cross-sectoral entry point for integrated policy uptake.

Future research should prioritize field-scale pilot studies to validate laboratory findings under real-world hydrodynamic, climatic, and ecological conditions. Long-term monitoring is essential to assess biodegradation rates, seasonal resilience, and vegetation colonization on and around the mats. Exploring hybrid configurations that combine WH fibers with other locally sourced materials, such as jute, coir, or bamboo—may further optimize mechanical performance and environmental sustainability. Additionally, embedding WH-based solutions within community-led erosion control programs could strengthen local ownership and foster decentralized climate adaptation.

As global interest in nature-based flood and erosion mitigation grows, context-specific innovations such as WH geotextiles offer a compelling entry point for sustainable adaptation in ecologically vulnerable, low-income delta regions. Their application in the Vietnamese Mekong Delta exemplifies a low-carbon, locally adapted NbS with potential relevance for other tropical and subtropical riparian systems worldwide.

5. Conclusions

This study evaluated the potential of WH geotextiles as an environmentally friendly, low-cost solution for small-scale riverbank protection in the Vietnamese Mekong Delta. Laboratory experiments demonstrated that the geotextiles significantly reduced sediment loss by lowering turbidity levels and effectively dissipated wave energy, achieving a wave height reduction of approximately 35–40%. Mechanical tests revealed that both the weaving pattern and the presence of adhesive coating strongly influence tensile strength and elongation. Among all configurations, the fish bone pattern with adhesive coating exhibited the highest tensile strength (8.36 kN/m after 12 wet–dry cycles), while uncoated geotextiles displayed superior elongation (up to 61.67%), indicating higher flexibility.

The combination of these characteristics highlights the ability of WH geotextiles to withstand dynamic hydraulic conditions while maintaining sufficient durability and adaptability. Beyond their technical performance, the use of WH fibers supports ecological sustainability by utilizing an invasive plant species that is abundant in the Mekong Delta, thus reducing waste and promoting circular resource use.

To support implementation, partnerships with local water management agencies, farmer cooperatives, and vocational training centers could facilitate knowledge transfer and upscaling. Integrating WH geotextiles into pilot programs under existing disaster risk reduction (DRR) or rural development schemes may provide proof of concept for wider policy adoption.

Moreover, as authors note, importantly, green geosynthetics must undergo rigorous performance evaluation under context-specific hydrological regimes, underscoring the need for field-based trials of WH mats under seasonal variability and real-world conditions [20,27,28]. Therefore, future studies should focus on large-scale field applications to validate laboratory findings and assess the long-term performance of WH geotextiles under natural conditions. Priority areas include systematic evaluation of biodegradation rates under varying hydrological regimes, monitoring of permeability retention and clogging potential, and assessment of vegetation colonization on and around the mats. In parallel, further material optimization, such as hybrid fiber blends or eco-friendly coatings, could enhance both mechanical properties and longevity. Addressing these factors will be essential to confirm the real-world feasibility and ecological integration of WH geotextiles as a viable, locally adapted NbS for erosion control in the VMD and other tropical deltas facing similar socio-environmental challenges.