Levees Research Articles

Water Potential Management and Arrangement of River Estuary Area for the Mitigation of the Climate Change in Bali

The impact of climate change in the form of rising temperatures, rising water levels, water pollution and extreme climate events are vulnerable to the potential of water resources in various sectors of life. The aim of this research is to build a method for managing water potential in river estuaries and arrangement the river estuary area for mitigation of the effects of climate change on water resources in the estuary area, especially in Bali. The method of this research is qualitative research on phenomenology that is happening. Data is collected in the form of primary data and secondary data. Primary data consists of environmental conditions in river estuaries related to climate change that occur, while secondary data in the form of water potential, water quality and land changes are obtained from various related instances. The results of the research found that watersheds on Bali Island are potential watersheds that can be used as raw water sources for both clean water and irrigation water. However, changes in land functions and climate change can cause some negative impacts on the potential and environmental conditions of estuary water resources such as floods, droughts, landslides, pollution of water by pollutants and sedimentation. Mitigation actions that must be taken to reduce the risk for the condition of water resources in river estuaries in Bali due to climate change are managing water potential by managing water systems, conducting water-saving campaigns, integrated management of water availability and needs, environment-based management, strengthening institutions in management of water resources, and the need to regulate cropping patterns right in the river estuary. While in terms of arrangement river estuary area there are several mitigation actions that can be carried out such as the construction of dikes around the estuary area, the construction of reservoirs, the construction of monitoring posts for river estuary conditions and the preservation of deforested areas around river estuary.

GIS-Based Flood Mitigation of Deli River

Structural actions to reduce floods such as the construction of reservoirs, dikes or dams are considered incapable of fully controlling the floods. Hence, information on flood risks through flood risk map is an obligatory to prevent and minimize losses caused by the floods. Regulation of Minister of Home Affairs no. 33 of 2006 on general guidelines for disaster mitigation states that one of the important things in disaster mitigation is the availability of information and map of disaster prone areas for each type of disaster. This study aimed to determine the potential and risk of flooding in Deli River by integrating software of Hydrologic Engineering Center-River Analysis System (HEC-RAS) with Geographic Information System (GIS). The design debit calculation conducted in four periods, 10, 25, 50 and 100 years. There are four districts, Medan Labuhan, Medan Marelan, Medan Deli and Medan Belawan, discovered as flood-prone areas. 14 sub-districts from four districts are potentially impacted by floods, namely Kota Bangun, Titi Papan, Tanah Enam Ratus, Rengas Pulau, Paya Pasir, Labuhan Deli, Besar, Martubung, Sei Mati, Pekan Labuhan, Nelayan Indah, Belawan Pulau Sicanang, Belawan Bahagia, and Belawan Bahari. Four evacuation points and 14 alternative paths also obtained based on the flood mapping.

Appropriate management practices help enhance odonate species richness of small ponds in peri-urban landscapes

Adult odonate biodiversity was investigated to understand their relationship with pond management practices and environmental conditions in a rapidly urbanized landscape. Twenty-four farm ponds in Taoyuan City were selected and classified into five pond groups based on pond management practices. In total, 21 species, 17 genera, and 6 families of odonates were recorded for a total of 5701 individuals between June 2014 and July 2015. The abundance of Odonata was unrelated to pond size or distance to the nearest pond; however, odonate species richness was negatively and significantly correlated with pond size. Pond management practices considerably affected pond aquatic macrophytes and dike construction materials. Ecology park ponds under intense human management and undisturbed ponds without any human management had higher species richness than did the ponds in the other three fish farming groups. Species richness was highest in small and human-modified ponds. By contrast, species richness was lowest in two fish farming pond groups. These results suggest that pond management practices can increase or reduce odonate species richness depending on the alteration of pond microhabitat features. Our observations suggest that the enhanced habitat quality of small ponds provides an opportunity to protect freshwater biodiversity for local governmental civil servants in urbanized landscapes.

Faunal change of macrobenthos in Ariake Sea during 20 years after the construction of dike for the Isahaya Reclamation Project

Faunal change of macrobenthos in Ariake Sea during 20 years after the construction of dike for the Isahaya Reclamation Project

Effects of repeated hydraulic loads on microstructure and hydraulic behaviour of a compacted clayey silt

Soils used in earth construction projects are mostly unsaturated, and they undergo frequent drying–wetting cycles (repeated hydraulic loads) due to changes in climatic conditions or variations of the ground water level, particularly at shallow depths. After compaction, changes in water content can significantly influence the hydromechanical response of the construction material, which therefore must be assessed for repeated hydraulic loads. This research investigates the effect of such loads on the microstructure and hydraulic behaviour of a silty soil, typically used in the construction of embankments and dykes, with the aim of providing a better understanding of the consequences of drying–wetting cycles on the response of the material over time. Experimental tests were performed to study the impact of drying–wetting cycles on the water retention, hydraulic conductivity, and fabric of compacted specimens. Fabric changes are documented to take place even without significant volumetric strains, promoting an irreversible increase in the hydraulic conductivity and a reduction in the capacity to retain water compared to the as-compacted soil. The fabric changes are interpreted and quantified by means of a hydromechanical model, which accounts for the evolving pore-size distribution at different structural levels. The proposed model reproduces quite well the microstructural observations, together with the evolution of the water retention behaviour and hydraulic conductivity.

A two-step approach to incorporate cut-off grade and stockpiling in oil sands mine planning optimization framework

In achieving maximum benefit in oil sands mining, the time and sequence of removing ore, dyke material and waste from the final pit limit is essential to the long-term production schedule. In-pit waste management strategy requires the simultaneous construction of dykes with the advancement of mining operations. This paper seeks to determine: (1) the time and sequence for removal of ore, dyke material and waste to maximize Net Present Value (NPV); (2) the quantity of dyke material required for dyke construction to minimize construction costs; and (3) the impacts of stockpiling and stockpile reclamation with limited time duration. An Integrated Cut-Off Grade Optimization (ICOGO) model was used to generate an optimum cut-off grade policy and a schedule for mining ore and waste, as well as overburden, interburden and tailings coarse sand dyke materials in long-term production planning. Subsequently, a Mixed Integer Linear Goal Programming (MILGP) model was developed to generate a detailed production schedule for removal of ore, waste and dyke materials from the final pit limit. The cut-off grade profile and schedule generated by the ICOGO model are used as guides to define the grade constraints and production goals required by the MILGP model. The developed models feature stockpiling with limited duration for long-term production scheduling. The models were applied to an oil sands case study to maximize the NPV of the operation. In comparison, whereas the ICOGO model solved the optimization problem faster, the MILGP model results provided detailed mining-cut extraction sequencing for practical mining.

Adapting to the sea: Human habitation in the coastal area of the northern Netherlands before medieval dike building

Before medieval dike building, the coastal area of the northern Netherlands was a wide, regularly inundated salt-marsh area. Despite the dynamic natural conditions, the area was inhabited already in the Iron Age. The inhabitants adapted to this marine environment by living on artificial dwelling mounds, so-called terps. Terp habitation was a highly successful way of life for over 1500 years, and may be re-introduced as a useful strategy for present and future communities in low-lying coastal regions that are facing accelerated sea-level rise. This already has been recommended in several reports, but detailed knowledge of the technology of terp habitation is usually lacking. The aim of this paper is to present nearly two decades of archaeological research in the coastal region of the northern Netherlands, in order to inform the current debate on the possibilities of adapting to the effects of climate change in low-lying coastal areas. It presents the multi-disciplinary methods of this research and its results, supplying details of terp construction and other strategies such as the construction of low summer dikes that are still useful today. The results and discussion of the presented research also make it possible to describe the conditions that must be met to make terp habitation possible. Terp habitation could have continued, were it not for the considerable subsidence of inland areas due to peat reclamation. That made the entire coastal area increasingly vulnerable to the sea. In response to this threat, dike building began in the 11th or 12th century, but these increasingly higher dikes decreased the water storage capacity and caused impoundment of seawater during storm surges. Moreover, accretion through sedimentation was halted from then on. Unlike terp habitation, the construction of high dikes therefore cannot be considered a sustainable solution for living in low-lying coastal areas in the long term.

Impact of gate operating modes of sea dikes on hydrodynamic regime and inundated area in Can Gio Bay

ABSTRACT Ho Chi Minh City gets severely inundated by upstream flooding and a combination of rising spring tides and rain, owing to the combined impacts of rapid urbanization and sea level changes. A sea dike to close Can Gio Bay has been proposed to regulate storage and control water levels in the drainage and sewer system of Ho Chi Minh City. However, this proposed sea dike and different gate operating modes could significantly change the hydrodynamic regime in Can Gio Bay. In this study, a two-dimensional hydrodynamic model was developed to assess changes in the hydrodynamic regime after construction of the sea dike, including fluctuations in the inundated areas in Can Gio Bay mangrove forests. The results show that sea dike construction is an effective solution for controlling water levels and reducing inundation, especially considering a sea level rise scenario in the year 2050. Further, the gate operation mode also affects the effectiveness of inundation reduction, which is approximately 10% better than the same sea dike type without gate operation. However, the sea dike was less effective in a sea water level rise scenario in 2100 for all scenarios.

Trophic Structures of Two Contrasting Estuarine Ecosystems With and without a Dike on the Temperate Coast of Korea as Determined by Stable Isotopes

To evaluate the modification of carbon flow in estuarine systems by a dike construction, we compared the trophic structures of the macrobenthic food webs in two contrasting estuaries, one with and one without a dike, on the western and southern coasts of Korea, by measuring the δ13C and δ15N values of subtidal macrobenthic consumers. The isotopic values of most organic matter sources were similar between the two estuaries, but there was a different pattern in the isotopic spatial variability between them. For the consumer δ13C values in the diked estuary, there were no significant spatial differences among sites and the isotopic niche widths were much narrower than those in the dike-free estuary. Moreover, the indices of community-wide metrics were smaller in the diked estuary than in the dike-free estuary. These results suggest a lower trophic diversity of macrobenthic consumers with their increased trophic redundancy in the diked estuary. These differences between the dike and dike-free estuaries might be explained by the decrease of benthic producers and then their lower food availabilities for consumers resulting from the presence of the dike. Our findings provide evidence that dike construction and subsequent alteration of hydrologic and circulation processes may lead to modification of the trophic structure of estuarine macrobenthic communities.

Intensification of the Ash Impoundment and its Stability Analysis

The paper presents specific example of method of intensification of ash impoundment. The impoundment for permanent bedding of ashes is situated on the left side of the Danube river. Part of the dam system of impoundment is based upon the original flood bank of Danube river. At the selection of materials for elevation of the impoundment, the decision was made primarily according to two indicators with an economic aspect – the transportation distance and the increase of the accumulation volume of the impoundment. Finally, the decisive criterion was the occurrence of the failure rate of the ash dam systems in comparison with the dams built from loess soils. As the impoundment is situated in the immediate vicinity of the Danube river, safe and failure-free operation has the priority. There is compared the geotechnical characteristics of the loess soils in the original deposition and the loess soils compacted at optimum water content by Proctor Standard compaction test. The proposed method of intensification of ash impoundment is analyzed. The stability analysis provides an example of the utilization of the results of the monitoring of the geotechnical properties of the materials forming the impoundment’s body and the surrounding rock mass.

ADAPTATION ASSESSMENT TO FUTURE BEACH LOSS DUE TO SEA LEVEL RISE IN THAILAND

Coastal erosion induced by seal level rise could become more serious problems worldwide (Hinkel et al., 2013; Udo and Takeda, 2017). There has been recent study regarding the projection of future (2100) erosion due to SLR in Thailand according to Intergovernmental Panel on Climate Change’s (IPCC) projection of SLR based on representative concentration pathway (RCP) scenarios. By overall, Thailand sandy beach areas are projected to be lost approximately 46% (RCP2.6) to 72% (RCP8.5) of its current condition (Ritphring et al., accepted) and the plan for its adaptation should be devised. Among variety of management strategies used for coastal protections, Yoshida et al. (2014) proposed a framework for a proper beach nourishment considering beach roles of environment conservation and recreation use and applied for Japanese beaches. Meanwhile, dike construction was adopted as an option in a global scale (Hinkel et al., 2013). Since there is no applicable adaptation framework to Thailand, this study provides a new framework to adapt to the sea level rise by cost-benefit analysis considering beach nourishment and dike construction as adaptation options.

EFFECTS OF WAVE LOAD ON THE LONG-TERM VEGETATION DEVELOPMENT AND THEIR RESISTANCE AS GRASS REVETMENTS ON SEA DIKES

Construction and design processes of revetments, sea dikes and estuarine dikes along the German coastline adhere the paradigm to protect and safeguard reliably the coastal hinterland from wave attack and storm surges. Following these standards coastal protection structures provide only poor ecosystem services in any proper design or maintenance approach. As a result, the EcoDike-project has been started with the aim to quantify and enhance the ecosystem services of revetments, sea dikes and estuarine dikes while preserving or possibly even enhancing the existing safety standards. Therefore, a profound understanding of the complex long-term interactions between wave load and vegetation development on sea dikes is inevitable. To achieve these objectives a typical seadike in prototype scale is tested under realistic and long-term wave loading in the new outdoor wave basin at the Ludwig-Franzius-Institute in Hannover (Germany).

Spatiotemporal variability in a copepod community associated with fluctuations in salinity and trophic state in an artificial brackish reservoir at Saemangeum, South Korea.

Saemangeum Reservoir in South Korea is an estuarine system enclosed by a dyke construction, where seawater inflow and retained water outflow are managed by the opening/closing of sluice gates installed in the southern part of the dyke. An exchange of the reservoir water can cause spatiotemporal fluctuations in the salinity and trophic state, which are major drivers determining variation in the composition of biological communities in estuarine systems. Here, we investigated the seasonal and spatial variability in the copepod community and environmental conditions (water temperature, salinity, transparency, chlorophyll a concentration, total nitrogen, total phosphorus and Carlson’s trophic state index) based on seasonally conducted field monitoring in the Saemangeum Reservoir from July 2013 to January 2018. In addition to the role of temperature, salinity and chlorophyll a concentration in structuring the copepod community and diversity, the biological indices of copepods with respect to salinity range and trophic state, were evaluated. The spatiotemporal variability in the salinity and trophic state variables showed contrasting patterns, and chlorophyll a concentration was negatively affected by salinity, indicating that the reservoir water was being highly exchanged with opening of the sluice gates. The mean trophic state index values, however, were constant in the eutrophic state (50―70). Dominant copepods were Acartia (A. hudsonica, A. sinjiensis, Acartia spp.) and Oithona (O. davisae and Oithona spp.), which are common species in eutrophic neritic water. Variation in the copepod community was mainly associated with the seasonal succession of the dominant species rather than a spatial gradient (from around the estuary to the sluice gates); however, site-specific differences in frequencies of several non-dominant species could be detected around the estuary (Sinocalanus tenellus) and the sluice gates (Centropages spp., Tigriopus spp. and Labidocera rotunda). The copepod diversity increased with species-richness from around the estuary to the sluice gates, which could result from variation in the site-specific location of non-dominant species. The frequency of particular species was also able to discriminate in terms of the salinity range (oligohaline: A. pacifica, S. tenellus and A. sinjiensis; mesohaline: Pseudodiaptomus inopinus; and polyhaline: C. abdominalis and Centropages spp.) and the trophic state (mesotrophic: C. abdominalis, Calanus sinicus and Centropages spp.; and hypereutrophic: S. tenellus, P. inopinus and Sinocalanus spp.). The findings from this study not only identify the factors determining spatiotemporal variation in the copepod community in the Saemangeum Reservoir, but also expand the applicability of copepods as biological indicators of conditions associated with salinity range and trophic state in other enclosed estuarine systems.

Detailed Hydrodynamic Feasibility Assessment for Leque Island and Zis a Ba Restoration Projects

Numerous restoration projects are underway in Puget Sound, Washington, USA with the goal of re-establishing intertidal wetlands that were historically lost due to dike construction for flood protection and agricultural development. One such effort is the restoration effort within the Stillaguamish Delta, benefitting from the cumulative effects from the Leque Island and zis a ba restoration projects. The preferred restoration design calls for the removal of perimeter dikes at the two sites and the creation of tidal channels to facilitate the drainage of tidal flows. A 3-D high-resolution unstructured-grid coastal ocean model based on FVCOM was developed to evaluate the hydrodynamic response of the estuary to restoration alternatives. A series of hydrodynamic modeling simulations were then performed to quantify the hydrodynamic response of the nearshore restoration project, such as periodic inundation, suitable currents, and desired habitat/salinity levels. Sediment impacts were also examined, including the potential for excessive erosion or sedimentation requiring maintenance. Simulation results indicate that the preferred alternative scenario provides the desired estuarine response, which is consistent with the planned design. A decrease in velocities and bed shear in the main river channels was noted for the restored condition associated with the increased inundation of tidal flat area and reduced tidal flows through the main channels. High bed shear near the restored tidal channel entrances indicates that the inlets may evolve in size until equilibrium is established.

3D Numerical Study of the Flow Properties in a Double-Spur Dikes Field during a Flood Process

A 3D numerical model is developed to study the flow characteristics of a double-spur dikes field on Yangtze River during a flood process, which was presented by the variation of the flow condition. The model is based on Navier–Stokes (NS) equations, the porous medium method (PMM) is employed to treat the solid structures including the river bed surface, the volume of fluid (VOF) method is applied to track the motion of the water surface during the flood process, and large eddy simulation (LES) is adopted to capture the turbulence transport and dissipation. Using this model, the target reach’s flow field before the construction of double-spur dikes is simulated first, while the numerical results are compared to the field measurements on flow velocity and water surface level, and fairly good agreements are shown. Then, the model is applied to reproduce the hydrodynamic evolution during a flood process after double-spur dikes’ constructions, while the detailed 3D flow fields are obtained under some certain states with different submergence rates of the spur dikes; finally, the potential damage positions around these spur dikes are analyzed accordingly.

Investigating the restoration of Lake Urmia using a numerical modelling approach

Abstract We assessed the effectiveness of multiple hydrologic restoration scenarios for Lake Urmia, as well as the variation of its salinity regime under no intervention, using a 2D shallow water model. Tested scenarios, proposed by Urmia Lake Restoration Program Committee, include: Preservation of current lake status (no intervention), complete closing of Shahid Kalantari causeway, dyke construction in the southern part of Lake Urmia, water transfer from Zarrinehrood River to Siminehrood River and reduction of agricultural water consumption by best agricultural practices. Results indicate that neither the closure of the causeway nor the construction of the southern dyke would significantly improve lake conditions when compared to preservation of current lake status. The water transfer alternative doesn’t seem to have any effect on the current lake conditions either. However, the reduction on water diversions by improving agricultural practices in the lake's basin leads to a partial restoration of the lake in terms of water level, surface area and volume. If current conditions persist, salinity in the northern part of Lake Urmia will reach supersaturation levels (340 g/L), generating further salt deposits.

Impacts of rice intensification on rural households in the Mekong Delta: emerging relationships between agricultural production, wild food supply and food consumption

Rice intensification programs target poverty reduction and improved food availability in Asia. Vietnam adopted a rice intensification policy aimed at a rice surplus for export by the 1990s. The intensification policy replaced an annual wet season crop with two to three High Yielding Variety (HYV) rice crops a year. These multiple annual crops required changes in hydraulic systems in areas such as the Mekong Delta (MD) with the introduction of low and high dikes for wet season flood control and dry season irrigation. This study examines the impacts of rice intensification and hydraulic changes in the MD between the 1990s and 2000s on rural household food sources, both wild and cultivated. Across study sites representing three flood management regimes, 165 households were sampled for data on household demographics, the collection and consumption of fish, other aquatic animals, wild and cultivated vegetables and fruit, and other food sources. The results indicate that rice intensification programs and dike construction have significantly increased rice production. However, farm household catch, collection and consumption of wild foods has decreased. Household use of wild fish, other aquatic animals, and wild vegetables was reduced significantly over the period. Significant wet and dry season variation in food availability emerged. Poor households experienced most loss. Overall household food security was affected. This study suggests that rice intensification policies aimed at global food security need to balance wider population access to a food staple with the need for rice farming communities to maintain access to high quality wild foods obtained from the fields and waterways of rice farming landscapes.

Short-Term Effects on Diversity and Biomass on Grasslands from Artificial Dykes under Grazing and Mowing Treatments

SummaryFew studies document the impacts of conservation management practices such as extensive grazing or mowing on the new ecosystems created by industrial conversions. In southern France, the Rhône channelling led to the construction of dykes to protect the Tricastin industrialized area from floods. Aiming to control plant dynamics for safety reasons and to favour plant biodiversity, mowing or extensive grazing by cattle were recently tested. Monitoring from both permanent plots and aerial photographs shows that three years of extensive grazing and annual mechanical mowing have modified plant composition, significantly increasing plant species richness, evenness and heterogeneity. The increase in evenness and beta-diversity from grazing was significantly higher than from mowing. Only grazing was able to reduce the height and cover of the dominant tussock perennial grass species (Brachypodium phoenicoides), while increasing bare soil cover and thus the contribution of annual species. The Normalized Difference Vegetation Index (NDVI) obtained through aerial photographic analyses confirmed the correlation between NDVI, aboveground biomass and plant species richness for the grazed site alone, allowing the results obtained from quadrats to be generalized to the scale of the grazed site. On the Rhône’s artificial dykes, extensive grazing appears to be a better management tool than mowing to enhance plant biodiversity and meet safety objectives.

Assessing the Resilience of Coastal Wetlands to Extreme Hydrologic Events Using Vegetation Indices: A Review

Coastal wetlands (CWs) offer numerous imperative functions that support a diverse array of life forms that are poorly adapted for other environments and provide an economic base for human communities. Unfortunately, CWs have been experiencing significant threats due to meteorological and climatic fluctuations as well as anthropogenic impacts. The wetlands and marshes in Apalachicola Bay, Florida have endured the impacts of several extreme hydrologic events (EHEs) over the past few decades. These extreme hydrologic events include drought, hurricane, heavy precipitation and fluvial flooding. Remote sensing has been used and continues to demonstrate promise for acquiring spatial and temporal information about CWs thereby making it easier to track and quantify long term changes driven by EHEs. These wetland ecosystems are also adversely impacted by increased human activities such as wetland conversion to agricultural, aquaculture, industrial or residential use; construction of dikes along the shoreline; and sprawl of built areas. In this paper, we review previous works on coastal wetland resilience to EHEs. We synthesize these concepts in the context of remote sensing as the primary assessment tool with focus on derived vegetation indices to monitor CWs at regional and global scales.

APPLICATION OF ADVANCED MECHANICAL MODELS FOR DESIGN AND CONSTRUCTION OF DIKES, REVETMENTS, EMBANKMENTS AND PORT YARD IN NAM DINH VU - HAI PHONG AREA

To apply advanced models for design and construction of dykes, revetments, embankments and port yard in Nam Dinh Vu - Hai Phong area, it is necessary to determine parameters of these models such as Hardening Soil Model (HS) and Soft Soil Model (SS). These can be determined through correlation parameters by available soil test as the fastest approach if we do not have direct experiments. This article defines and predicts the soil characteristics of the HS and SS in Nam Dinh Vu site, additionally it introduces the application of these parameters to the design of a typical dike section of Nam Dinh Vu dike.