INTRODUCTION
Introduction
Vietnam has 2360 rivers and canals that have 220000 km in length Only about 19%
Approximately 41,900 km of waterways are considered navigable, with about 7% (15,436 km) managed under specific frameworks (Luis C Blancas and M Baher El-Hifnawi, 2014) Our country’s tropical monsoon climate results in frequent heavy rainfall, highlighting the vital role of floodplains—areas adjacent to rivers, lakes, ponds, and oceans that periodically experience flooding Floodplains are ecologically productive and environmentally sensitive zones that perform essential natural functions such as water storage, conveyance, water quality protection, and groundwater recharge Moreover, they provide critical habitats for fish and other wildlife, supporting biodiversity and ecosystem health.
Land cover change, driven by human demand, can significantly impact floodplains, especially floodplain wetlands of large rivers These vital ecosystems have been increasingly affected by anthropogenic activities such as draining, land conversion, and chemical and physical alterations caused by land and water management practices Such changes threaten the health and stability of floodplain environments, emphasizing the need for sustainable management strategies.
In 2007, increased human activities such as clearing riverbank land for farming, vegetable cultivation, and animal husbandry significantly impacted adjacent river areas The construction of infrastructure like bridges and buildings further altered the natural landscape As population growth intensified, the demand for land led to encroachment on floodplains, often for personal or agricultural purposes, highlighting the pressure on river ecosystems and the need for sustainable land use management.
Floodplain development poses significant threats to water quality, storage capacity, and natural habitats of aquatic life, while increasing the risk of flooding Unregulated development, especially in flood-prone areas, can lead to severe economic disruptions and loss of human lives during flood seasons In Vietnam, managing floodplains is challenging due to unclear strategies, exemplified by incidents in Gia Vien district where over ten yards for manufacturing and trading within the outer dike narrow the Hoang Long River and cause traffic gridlocks, threatening flood safety (Van Phuc and Tien Khanh, 2016) Similarly, in Phu Tho province, illegal construction by Northwest Mineral Corporation within floodplains, disregarding local authority orders, highlights the lack of interest and poor enforcement in floodplain management (Bui Anh, 2016) These examples underscore the urgent need for effective floodplain management strategies to prevent environmental degradation and safeguard communities.
Bui River is a 91-kilometer-long tributary of the Day River, with a basin area of 1,249 km², originating from Lam Son commune in Hoa Binh province and flowing into Phuc Lam commune in Hanoi before merging with the Day River (Nguyen Thuy Duong, 2016) Over time, the Bui River catchment has experienced significant land use and land cover changes, which have impacted its flood regime and floodplain development Despite these changes, there have been no existing studies on how land use and cover changes have affected the hydrological conditions and floodplain dynamics in the Bui River This study aims to investigate these impacts through an analysis titled “Floodplain development in Bui River due to land-use change from 2004 to 2015.”
Literature review
1.2.1 Introduction of GIS, HECRAS and HEC-GeoRAS
A Geographic Information System (GIS) is an information system that utilizes spatial data inputs, databases, and outputs to analyze and visualize geographic information GIS plays a crucial role in supporting natural resources planning and management, enabling more efficient urban development It also facilitates the storage and retrieval of administrative information, enhancing decision-making processes in various fields.
GIS has five main components, including:
Hardware: is the computer on which a GIS operates
Software: provides the functions and tools needed to store, analyze, and display geographic information
Data: is the most important component of a GIS which are geographic data and related tabular data
People: plays important role to manage the system and develop plans for applying it into real-world problems
Methods: are the models and operating practices unique to each organization
Applying GIS in floodplain management is an efficient method for constructing inundation maps, as these maps provide critical information on flood levels and inundation areas Such data is essential for effectively informing citizens about flood risks and minimizing the potential consequences of flooding.
HEC-RAS, developed by the Hydrologic Engineering Center of the U.S Army Corps of Engineers, is a comprehensive hydrologic modeling system designed to simulate the physical properties and flow routing of streams and rivers This advanced software features a user-friendly graphical interface, integrated database, and data management tools, enabling accurate analysis of natural and artificial water flows With HEC-RAS, users can effectively visualize hydrologic characteristics such as water depths and inundation areas, making it an essential tool for floodplain management, hydraulic analysis, and water resource planning.
HEC-GeoRAS is an effective tool that integrates GIS data with HECRAS within the ArcGIS interface, facilitating comprehensive flood modeling and analysis It utilizes inputs such as DEM, infrastructure maps, land use, and land cover data to accurately construct inundation maps These detailed flood maps enable researchers and policymakers to assess the spatial extent of flooding events and predict potential impacts Additionally, HEC-GeoRAS helps in calculating the monetary consequences of floods, supporting cost-effective disaster management and mitigation planning.
1.2.2 Application of GIS, HECRAS and HEC-GeoRAS in modeling floods
Recent advancements in GIS tools and techniques have significantly enhanced river engineering applications Researchers such as Gert A Schultz (1995), Yuyan C Jordan (2012), Holgẻ Cammerer et al (2013), Dimitrios Alexakis et al (2013), and M Yu et al (2015) have successfully employed GIS to analyze and assess changes in flood characteristics resulting from land use modifications Similarly, Jie Liu, Shao-yu Wang, and Dong-mei Li have contributed to this field, demonstrating the critical role of GIS in understanding and managing flood risks associated with land use changes.
In 2014, researchers analyzed the impact of land-use changes on flood exposure in Wuhan within the Yangtze River basin Nguyen Hieu Trung also evaluated urban water management utilizing GIS technology Several commercial software packages now integrate GIS with hydraulic modeling for comprehensive spatial analysis, such as Abolghasem et al (2014) Notably, the HEC-RAS software by the Hydrologic Engineering Center allows for seamless integration with ArcGIS through HEC-GeoRAS, enhancing flood modeling capabilities.
Abolghasem Akbari, Golamali Mozafari, Mohsen Fanodi, and Maliheh Sadat Hemmesy (2014) utilized ArcGIS and HEC-RAS to identify floodplain areas based on flood frequency and evaluate changes in floodplain boundaries over 50 years due to land-use modifications Meanwhile, Karl-Erich Lindenschmidt, Apurba Das, Prabin Rokaya, and Thuan Chu (2015) combined ArcGIS and HEC-GeoRAS to conduct a comprehensive ice jam flood hazard assessment for the Town of Peach River.
In Vietnam today, various hydrologic models like MIKE FLOOD, HECRAS, and WMS are widely used for flood research and management Each model offers unique advantages, allowing researchers to select the most suitable tools based on specific project requirements These models play a crucial role in understanding flood dynamics, enhancing predictive accuracy, and supporting effective flood mitigation strategies across Vietnam.
Luu Duy Vu and Nguyen Phuoc Sinh (2012) successfully applied the Water Management System (WMS) model to predict flooding in Da Nang city, demonstrating its effectiveness in flood forecasting Their research utilized the WMS model to analyze major floods in 2007 and 2009, helping to identify key model parameters and validate its accuracy for regional flood prediction This study highlights the practical application of WMS in urban flood management and disaster mitigation efforts.
- Application of MIKE FLOOD to show the flood scenarios in 2007 and 2009, written by
To Thuy Nga et al, in 2013 aims to find out the relationship between floods and climate change
Constructing inundation maps of downstream areas in the Vu Gia – Thu Bon basin (Tran Van Tinh, 2013) represents a significant effort that leverages advanced hydrological and hydraulic modeling using HEC-HMS, HEC-RAS, and HEC-GeoRAS The integration of these HEC models with GIS data enhances the accuracy and reliability of flood risk assessments in the region This comprehensive approach provides vital insights for effective flood management and disaster preparedness in the Vu Gia – Thu Bon basin.
In 2011, Pham Thi Kim Phung conducted a comprehensive study using the HEC-RAS model to define the floodplain in Dak Mi upstream She employed a one-dimensional hydraulic computational model to simulate current flow conditions and predict various flood scenarios The findings provided valuable insights for assessing floodplain areas upstream, enabling better flood alarm systems and informing re-planning and compensation activities to mitigate flood risks.
- Dang Dinh Duc (2012) researched on constructing vulnerable map for Nhue-Day river basin using MIKE FLOOD.
GOALS AND SPECIFIC OBJECTIVES
Goals
This study aims to examine the impact of land-use/cover change on floodplain in Bui river from 2004 to 2015.
Specific objectives
- To investigate the hydrological conditions and land use/cover change in Bui River during the period of 2004-2015;
- To evaluate the dynamics and extent of floodplain in the relationship with changes of land use/cover and hydrological conditions along the Bui River;
1) How does the hydrological conditions in Bui river change from 2004 to 2015?
2) What are the changes of land-use/cover in Bui river basin from 2004 to 2015?
3) Does land-use change have any influences on floodplain of Bui river?
STUDY AREA AND METHODS
Selection of research site
Figure 3.1 Map of study area
The study site encompasses the Bui River and its basin, spanning from Lam Son commune in Luong Son district, Hoa Binh province, to Xuan Mai town in Chuong My district, Hanoi It includes seven administrative units: Lam Son, Tan Vinh, Nhuan Trach, Hoa Son, Luong Son, Xuan Mai, and Thuy Xuan Tien, covering a diverse geographical area crucial for ecological and hydrological research.
- Dan Hoa commune (Ky Son district, Hoa Binh) in the west,
- Phu Man (Quoc Oai district, Hanoi) in the north,
- Cao Ram (Luong Son district, Hoa Binh) in the south,
- Dong Son (Chuong Mi district, Hanoi) in the east
The study site is located in a semi-mountainous, semi-plain area characterized by uneven and hilly terrain, serving as a transitional zone between the delta and midland regions Its diverse landscape, featuring low mountains and hills, creates bumpy fields that support agricultural activities The relatively low average elevation of these hills and mountains offers favorable conditions for the development of both forestry and farmland.
The Bui River Basin experiences a tropical monsoon climate characterized by distinct seasonal variations This climate is influenced by the Northeast and Southeast monsoons, with the Northeast monsoon dominating from November to March and the Southeast monsoon from April to July Additionally, the Southwest monsoon also impacts the region's climate, contributing to its seasonal patterns These climatic conditions significantly shape the area's natural resources and ecological environment.
Soil resources: The main components of soil are yellow-brown Feralit developed on
Foocfiarit rock In addition, alluvium is deposited by virtue of river and stream system
Luong Son district, including Luong Son town, Lam Son, and Tan Vinh communes, is rich in mineral resources such as limestone, building stone, clay, basalt, and polymetallic ores Notably, there is an abundant source of clay in Xuan Mai town, which is ideal for producing bricks and tiles These mineral resources present significant economic potential for local development and industrial applications.
Historically, natural forests in Tan Vinh, Lam Son communes, and Luong Son town were rich in diverse and valuable woody species However, extensive artificial activities have led to significant deforestation, resulting in the replacement of primary forests with secondary forests Currently, these forests are primarily utilized for production purposes, with only a small portion designated for protection and special uses In contrast, forests in Xuan Mai town are mainly dedicated to research and study, highlighting different regional management and usage practices.
Located near Hanoi, this destination offers a strategic position with scenic mountainous terrain and access to natural river systems, making it ideal for ecotourism, resorts, and golf courses Visitors can also explore cultural tourism attractions, such as the Muong cultural village in Tan Vinh commune, enriching their experience with local traditions and heritage.
The Bui River Basin has experienced rapid population growth driven by its favorable natural conditions, according to annual statistics from local administrations The region's economic landscape is shifting, with an increasing focus on industrial and service sectors while agriculture declines This economic transition encourages local communities to alter land cover and utilize land resources strategically, particularly near the main flow of the Bui River, to meet evolving developmental demands.
Methods
Secondary data collection is a crucial initial step in developing a computational model Essential data includes a land use database for the study area from 2004 to 2016, along with a Digital Elevation Model (DEM) of the Bui River basin, obtained from the USGS GDEX platform Hydrometeorological data from Lam Son station, located upstream of the Bui River, encompasses flow discharge and rainfall measurements from 2004 to 2015, with rainfall data recorded daily using Vietnam rain gauges Additionally, flow discharge during the study period was calculated by staff at Lam Son station, utilizing cross-sectional data as detailed in figure 3.4.
Aiming to assess the floodplain development, ten cross sections along Bui river had chosen and investigated as illustrating in the diagram below:
Water level and water surface elevation were measured in different locations in Bui River using transect and cross-sections by following steps:
1) Elevation and geographic locations (longitude, latitude) of each field site were measured by using GPS
2) River bathymetry and flow discharge were collected separately in each cross section (Figure 3.2) The data will be collected in Table 3.1
Figure 3.4 Example of cross-sectional measurement
Float is an inexpensive and simple method which can be used to measure surface velocity
To effectively use the float method, gather essential tools including a tape measure, stopwatch, and a meter stick to accurately measure depth Additionally, you’ll need at least three highly visible buoyant objects, such as oranges, that are buoyant enough to remain unaffected by wind Stakes are also necessary to securely anchor the tape measure to stream banks, ensuring precise and reliable measurements during the process.
Step 1 Identify the highest point in stream bed belonged to the cross section
Step 2 Mark the start and end point perpendicularly with your cross section in which distance from the start to end point is 5 meters
Step 3 Drop your object into the stream in the start point on time of starting the watch
Step 4 Stop the watch when the object crosses the downstream marker
Step 5 It is necessary to repeat the measurement at least 3 times and use the average in further calculations
V surface = travel distance/ travel time = L/t
Because surface velocities are typically higher than mean or average velocities, therefore
V mean = k V surface where k is a coefficient that generally ranges from 0.8 for rough beds to 0.9 for smooth beds (0.85 is a commonly used value)
Using collected data, we can accurately determine river bed elevation and bathymetry, providing insights into river morphology Additionally, flow discharge, which measures the volume of water passing a specific point within a given time, is essential for hydrological analysis Flow discharge depends on factors such as water velocity and the cross-sectional area of the stream, making it a key parameter for understanding stream flow dynamics and flood risk management.
Where Q is stream discharge (volume/time), A is cross sectional area, and V is flow velocity
The result of fieldwork is attached in Appendix 1
To create the land use map of the Bui River Basin, comprehensive land use data from Chuong Mi and Luong Son districts across different periods are essential This data is first imported into MapInfo for editing and smoothing to ensure accuracy The refined land use map is then transferred from MapInfo to ArcGIS using an FME converter The extraction process involves utilizing ArcGIS tools such as Arc Toolbox, Spatial Analyst, Extraction, and Extract by Mask to isolate the Bui River Basin land use information from the districts’ maps.
In order to find out the trend of floodplain development, four flood events which have equivalent rainfall during 2004-2016 were chosen, including: July 11 th 2006, June 21 st
2010, August 23 rd 2012 and September 25 th 2013
The process of floodplain mapping is described shortly in the following diagram:
Figure 3.5 Diagram of floodplain mapping process
Hydrological data (water discharge/water surface elevation)
ArcGIS, HEC-GeoRAS TIN model
RAS feature classes, including Stream Centerline, Main Channel Banks, Flow Path Centerlines, and Cross Section Cut Lines, are created in HEC-GeoRAS and imported into HECRAS for accurate river modeling For the TEST13092016 project, existing geometric data such as station, elevation, downstream reach length, Manning’s n values, and main channel bank stations were added and carefully edited to ensure comprehensive analysis Steady Flow Analysis in HECRAS calculates water surface profiles for steady, gradually varied flows, allowing simulation of water surface levels during different flood scenarios by modifying boundary conditions like normal depth, known water surface, and discharge HECRAS’s core principle relies on the positive correlation between water surface points along the river, ensuring precise flood modeling and risk assessment.
Figure 3.6 Profile plots of water surface for five flood events: July 11 th 2006, June
21 st 2010, August 23 rd 2012, September 25 th 2013
The water surface elevation profile for July 11th, 2006, was used to delineate the flooded areas along the Bui River floodplain Flood depth was determined by calculating the difference between water surface elevation and terrain elevation All cross sections along the Bui River were extracted within a 5-kilometer width to comprehensively cover potential floodplains These water levels were then assigned to each cross section to develop a Triangular Irregular Network (TIN) model, providing accurate flood modeling and analysis.
Figure 3.7 Triangular irregular networks (TIN) model of study site
The TIN model accurately represents the surface morphology of the flood water surface, specifically the water elevation during flooding events This model was converted into a raster format, assigning water surface elevation values to each pixel for detailed spatial analysis Next, the floodwater elevation model was subtracted from the digital elevation model (DEM) of the study area, allowing for the identification of floodplain zones Only positive differences were retained to delineate the floodplain along the Bui River These processing steps were consistently applied to generate floodplain maps for other flood events, providing a reliable tool for flood risk assessment.
RESULTS AND DISCUSSION
Characteristics of hydrological conditions and land-use/cover change in Bui river basin
4.1.1 Characteristics of hydrological conditions in Bui river from 2004 to 2016
Figure 4.1 The response of monthly rainfall and monthly discharge from 2004 to 2015
Flow regime in Bui river basin is divided clearly into two seasons: rainy season and dry season The rainy season starts from April to October, it takes from 78% (2007) to
89% (2004) of total annual rainfall Meanwhile, the dry season begins from November to March next year During the study period, the maximum monthly rainfall reached
559.8mm in September 2009 However, the minimum monthly rainfall was 0.5 mm in
M o n th ly r ai n fal l (m m )/ m o n th
M o n tl y d is c h ar ge (m m /m o n th )
The flooding season in the Bui River typically spans from May to October, with peak runoff occurring in July, August, and September, as indicated by discharge data from Lam Son station Annual runoff analysis shows that during the rainy season, between 58.4% (2008) and 88.5% (2011) of the total annual runoff occurs, highlighting the significant contribution of the rainy season to the river's overall water flow (Figure 4.1).
Figure 4.2 Relationship between annual rainfall and runoff in Bui river from 2004 to 2015
In the period from 2004 to 2015, the highest annual rainfall is 2608.1 mm in 2008 and the lowest one is 810.72 mm in 2004 (Figure 4.2) The runoff coefficient within
2004 – 2015 changes from 54.0% to 57.9% The relationship between annual rainfall
A n n u al r ai n fal l (m m /ye ar )
Annual runoff can be accurately estimated using the equation y = 0.6093x – 42.176, where y represents annual runoff and x represents annual rainfall The high coefficient of determination (R² = 0.9948) indicates that approximately 99.48% of the variability in annual runoff is explained by this model, demonstrating a strong correlation between rainfall and runoff (Figure 4.3) This relationship is essential for understanding hydrological patterns and managing water resources effectively.
Figure 4.3 Relationship between annual rainfall and runoff in Bui river from 2004 to 2015
4.1.2 Situation of Land-use in Bui river basin from 2004 to 2016
Based on land-use maps generated for 2005, 2010, and 2014 with support from MapInfo, the Bui River basin's land use was categorized into eight key types: agricultural land, residential areas, forest land, industrial zones, lakes and rivers, transportation systems, unused land, and other areas such as cemeteries, defense zones, educational facilities, and public service areas The statistical data on land-use changes over these years is provided in Appendix 2, illustrating significant trends with a high correlation coefficient (R² = 0.9948) in the regression analysis (y = 0.6093x - 42.176).
Figure 4.4 Land-use map of Bui river basin in 2005
Figure 4.5 Land-use map of Bui river basin in 2010
Percentage of land-use classes
Percentage of land-use classes
Figure 4.6 Land-use map of Bui river basin in 2014
Bui river basin is largely occupied by agricultural land, residential areas and forest Forest is almost located in riverhead, belonged to Lam Son and Hoa Son communes From
Between 2005 and 2014, Bui River's basin experienced notable land use changes, with forest land increasing by 9.15%, residential areas expanding by 1.38%, and industrial zones growing by 0.77% The transportation system was continuously upgraded by 0.74%, reflecting its vital role in connecting Hanoi and Hoa Binh province, home to key industrial zones Land use planning by local authorities led to a significant reduction in unused land by 6.55% and agricultural areas by 3.62%, indicating a shift towards more developed and efficient land utilization.
The fluctuation of land-use classes during 2005-2014 is depicted more clearly in the following chart:
Percentage of land-use classes
Figure 4.7 Fluctuation of land use categories in Bui river basin in 2005, 2010, 2014
The analysis of land-use/cover changes around the Bui River reveals significant expansion of impervious surfaces, particularly in large built-up areas near the main river channel These impervious areas include various land classes such as residential zones, industrial zones, transportation networks, cemeteries, defense areas, educational institutions, and public service facilities Land-use maps from 2005, 2010, and 2014 show that the percentage of total impervious area (%TIA) in the Bui basin increased from 25.57% to 28.21% and then to 29.59%, indicating a clear upward trend in impervious surface coverage over the study period This growth reflects urbanization and development trends impacting the basin’s land use.
4.2 Floodplain characteristics in Bui river for different flood events
Four flood events are chosen selectively due to equivalent amount of rainfall ArcGIS, HECRAS and HEC-GeoRAS are supportive software and tools to model floodplain successfully.
P er ce n tage o f lan d -u se c at ego ry( %)
Figure 4.8 Model of floodplain in Bui river in different flood events: a) July 11 th 2006, b) June 21 st 2010, c) August 23 rd 2012, d) September 25 th 2013
The correlation of rainfall, floodplain and water surface elevation in Lam Son station and total impervious area over time is summarized in the table below:
Table 4.1 Correlation of rainfall, water surface elevation, floodplain areas
The second, third and fourth cross sections are used to evaluate the change of floodplain in four different flood events that have the equivalent rainfall
Figure 4.9 Fluctuation of width and water surface elevation in cross section 2,3,4 in four flood events
Accurate floodplain modeling is essential for effective flood risk management In this study, observed widths from ten cross sections measured through fieldwork were compared to simulated widths, demonstrating the model's reliability The relationship between observed and simulated widths is represented by the equation y = x, indicating a direct correlation An R² value of 0.8879 confirms that the model achieves an accuracy of 88.79%, validating its effectiveness in floodplain analysis.
Figure 4.10 The relationship between experimental width and simulated width
4.3 Evaluation of the interactions between changes in land-use/cover, hydrological conditions and floodplain
This study evaluates the impact of land-use change on floodplains by analyzing four flood events with equivalent rainfall The selected events occurred on July 11th, providing consistent conditions for comparison Understanding these events helps to assess how land-use modifications influence flood severity and frequency within the region By focusing on floods with similar rainfall amounts, the research ensures accurate insights into the relationship between land-use changes and flood behavior.
2006, June 21 st 2010, August 23 rd 2012, September 25 th 2013 Therefore, it is compulsory to have land-use data of Bui river basin in 2006, 2010, 2012 and 2013 However, due to the
2016 lack of database, this study suggests a hypothesis based on the fluctuation trend of land-use planning
This hypothesis will be used to analyze the influences of land-use change on floodplain
Changes in land-use are categorized into modification and conversion; modification involves within-type changes like forest thinning, while conversion refers to transforming one land-use type into another, such as converting farmland into residential areas In the Bui river basin from 2004 to the present, the most notable changes include the expansion of built-up areas by replacing agricultural and unused lands and the increase of forest coverage in upstream regions The impervious surface area—comprising residential, industrial, transportation, and public service zones—has risen significantly from 25.57% in 2005 to 29.59% in 2014, leading to increased surface runoff due to reduced infiltration The reduction in agricultural land, a primary water source for irrigation, has contributed to rising water levels in the main channel Consequently, despite similar or decreasing rainfall levels during four flood events, water surface elevations at Lam Son station and floodplain areas continued to rise, indicating intensified flood risks.
Figure 4.11 The response of rainfall and water surface level in Lam Son station
Figure 4.12 The relationship between percentage of total impervious area and floodplain area in Bui river y = 4.9064x + 10.47 R² = 0.97 P = 0.015
Percentage of total impervious area (%)
P-value was 0.015 and smaller than 0.05 so it had great deal in statistics R 2 is nearly 1 then the hypothesis is acceptable (because the percentage of total impervious area in Bui river basin can not be much different in comparison with the given hypothesis; if it is a little different, R 2 is still nearly equal to 1) Therefore, it proves the total impervious area has close relationship with floodplain In other words, the land-use change plays significant role in floodplain development
4.4 Possible solutions to enhance corridor management for sustainable development
Aiming to reduce negative impacts of flood events in Bui river basin, this study also provides some possible solutions to enhance floodplain management for sustainable development
Increasing the resilience of river communities
The increasing population in floodplains is driven by their proximity to water supplies, fertile soils, and flat terrain To enhance the resilience of river communities, it is essential to address flood risks through both structural solutions, like levees and flood storage facilities, and non-structural measures such as advanced flood warning systems and effective regulatory policies Combining these approaches can effectively mitigate flood hazards and protect vulnerable communities.
Effective floodplain management requires a comprehensive long-term action plan that recognizes the ecological importance of natural floodplain ecosystems Implementing clear strategies is essential to reduce the risk of flood events and enhance water quality These approaches help balance environmental conservation with flood risk mitigation, ensuring sustainable and resilient floodplain systems.
- A growth in the mosaic character within the catchment/basin
- Extension of ecotone buffer zones that slow down the water run-off from a basin to river ecosystems and further restrict the transfer of pollutants
Implementing high-quality permeable technologies, such as partial permeable materials in construction, effectively increases surface permeability in river basins This approach reduces the land's water retention capacity over large areas, helping to improve water flow and prevent flooding Utilizing permeable materials in building infrastructure promotes sustainable water management and enhances the natural hydrological cycle in river basin areas.
- Increasing the water retention capacity by carrying out forestation
- Defining a restrictive limit for residential and economic development in river floodplains
Increasing human awareness and exchanging knowledge
By exchanging knowledge and experiences among scientists, public officials, and industry representatives, stakeholders will gain a deeper understanding of sustainable floodplain management This approach is essential for preventing encroachment activities that threaten the future integrity of floodplains Promoting collaboration and information sharing is vital for implementing effective floodplain conservation strategies and ensuring long-term environmental resilience.
Evaluation of the interactions between changes in land-use/cover, hydrological
This study evaluates the impacts of land-use change on floodplains by analyzing four flood events with similar rainfall patterns The selected flood events, all occurring on July 11th, provide a consistent basis for comparison By focusing on these comparable events, the research aims to accurately assess how land-use modifications influence flood behavior and floodplain dynamics under similar precipitation conditions.
2006, June 21 st 2010, August 23 rd 2012, September 25 th 2013 Therefore, it is compulsory to have land-use data of Bui river basin in 2006, 2010, 2012 and 2013 However, due to the
2016 lack of database, this study suggests a hypothesis based on the fluctuation trend of land-use planning
This hypothesis will be used to analyze the influences of land-use change on floodplain
Land-use changes can be classified into two categories: modification and conversion Modification involves altering the condition within a land cover type, such as forest thinning, while conversion refers to transferring land from one use to another, like turning farmland into residential areas In the Bui River basin from 2004 to the present, significant land-use changes include the conversion of agricultural and unused land into built-up areas and the expansion of forest land in the upstream region The impervious surface area—comprising residential, industrial, transportation, and public service zones—increased from 25.57% to 29.59% between 2005 and 2014, leading to higher surface runoff due to decreased infiltration The reduction in agricultural land, a primary water-consuming resource for irrigation, has caused water levels in the main channel to rise Despite nearly stable or decreasing rainfall during four major flood events, water surface elevations at Lam Son station and floodplain areas continued to increase, underscoring the impact of land-use changes on flood dynamics.
Figure 4.11 The response of rainfall and water surface level in Lam Son station
Figure 4.12 The relationship between percentage of total impervious area and floodplain area in Bui river y = 4.9064x + 10.47 R² = 0.97 P = 0.015
Percentage of total impervious area (%)
P-value was 0.015 and smaller than 0.05 so it had great deal in statistics R 2 is nearly 1 then the hypothesis is acceptable (because the percentage of total impervious area in Bui river basin can not be much different in comparison with the given hypothesis; if it is a little different, R 2 is still nearly equal to 1) Therefore, it proves the total impervious area has close relationship with floodplain In other words, the land-use change plays significant role in floodplain development.
Possible solutions to enhance corridor management for sustainable development
Aiming to reduce negative impacts of flood events in Bui river basin, this study also provides some possible solutions to enhance floodplain management for sustainable development
Increasing the resilience of river communities
Due to their proximity to water supplies, fertile soils, and flat landscapes, floodplains are increasingly inhabited, raising the risk of flooding in these areas To enhance the resilience of river communities, it is essential to implement both structural solutions, such as levees and flood storage facilities, and non-structural measures like advanced flood warning systems and effective regulatory policies Combining these approaches can effectively mitigate current flood risks and protect vulnerable populations.
Developing an effective long-term floodplain management plan begins with understanding the vital role of natural floodplain ecosystems Implementing clear strategies focused on reducing flood risk and enhancing water quality is essential These approaches help mitigate the impacts of flooding while preserving the health of floodplain ecosystems, ensuring sustainable development and environmental resilience.
- A growth in the mosaic character within the catchment/basin
- Extension of ecotone buffer zones that slow down the water run-off from a basin to river ecosystems and further restrict the transfer of pollutants
Implementing high-quality permeable technologies effectively enhances the permeability of river basin surfaces, reducing their capacity to retain water across large areas For example, utilizing partial permeable materials in the construction of houses and buildings promotes better water infiltration, helping to manage surface runoff and mitigate flood risks This innovative approach supports sustainable water management and flood prevention in river basin environments while maintaining eco-friendly development.
- Increasing the water retention capacity by carrying out forestation
- Defining a restrictive limit for residential and economic development in river floodplains
Increasing human awareness and exchanging knowledge
By fostering the exchange of knowledge and experiences among scientists, public officials, and industry stakeholders, awareness of sustainable floodplain management is significantly enhanced This collaborative approach is essential in implementing effective strategies to prevent encroachment, which poses a threat to the longevity and safety of floodplains Adopting sustainable floodplain management practices is crucial for protecting these vital ecosystems and ensuring their resilience against future flooding risks.
CONCLUSION AND RECOMMENDATIONS
Conclusion
This study concludes that the flow regime of the Bui River is divided into two seasons, with the runoff coefficient fluctuating between 54.0% and 57.9% from 2004 to 2015, and a strong correlation between annual runoff and rainfall described by the equation y = 0.6093x – 42.176 (R² = 0.9948) The total impervious area in the Bui River basin has increased from 25.57% to 29.59% due to land-use planning, while agricultural and unused lands decreased by 3.62% and 5.55%, respectively Despite consistent rainfall amounts, both the width and water surface elevation have increased, with a significant relationship between impervious area and floodplain area expressed by y = 4.9064x + 10.47 (R² = 0.97), indicating that floodplain development depends heavily on land-use, primarily due to infiltration processes To promote sustainable development, the study recommends solutions such as enhancing resilience of river communities, implementing ecohydrology planning, raising public awareness, and fostering knowledge exchange for effective corridor management.
Recommendations
This study successfully applies Hydrologic Engineering Center’s River Analysis System (HECRAS) and HEC-GeoRAS for flood hazard mapping in Vietnam, despite these tools being less known locally However, challenges such as limited hydrological data, low-resolution DEM images (30m x 30m), and gaps in knowledge, skills, and experience have affected the outcomes To improve accuracy and effectiveness, future research should focus on collecting comprehensive land-use planning data, increasing the number of river cross-sections, and enhancing user proficiency in advanced hydrological modeling technologies.
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Bui Anh, 2016 Phu Tho: Building house on stilts in the floodplain
Bui Duy Tan, Pham Van Lac, 2012 Applying MIKE model in flooding calculation of downstream of the Cude river basin, Da Nang city
Duong Dang Minh Phuoc, 2014 Inundation illustration in downstream of DakBla river by application of HEC-RAS model and HEC-GeoRAS tool
This study by Dimitrios Alexakis et al (2013) utilizes GIS and remote sensing techniques to assess the impact of land use changes on flood hydrology in the Yialias Basin, Cyprus The research highlights how land use alterations influence flood frequency and magnitude, emphasizing the importance of spatial analysis for effective flood management By integrating GIS data with remote sensing imagery, the study provides a comprehensive understanding of how urbanization and land cover modifications affect hydrological responses in the basin The findings demonstrate that land use change significantly increases flood risk, underlining the need for sustainable land planning This case study underscores the vital role of GIS and remote sensing tools in assessing environmental impacts and supporting flood mitigation strategies in vulnerable regions.
The 2007 open-file report by James Kriz, Don Huggins, Craig Freeman, and Jude Kastens titled "Assessment of Floodplain Wetlands of the Lower Missouri River Using a Reference-based Study Approach" offers a comprehensive evaluation of floodplain wetlands in the Lower Missouri River This study, published by the Kansas Biological Survey, employs a reference-based methodology to assess wetland health and distribution, providing valuable insights for conservation and management efforts The report emphasizes the importance of understanding floodplain wetland ecosystems to preserve biodiversity and restore natural hydrological functions With 63 pages of detailed analysis, it serves as a critical resource for environmental professionals and policymakers aiming to protect and sustain Missouri River floodplain wetlands.
Jie Liu, Shao-yu Wang, Dong-mei Li, 2014 The Analysis of the Impact of Land-use Changes on Flood Exposure of Wuhan in Yangtze River Basin, China 28, 2507-2522
Holger Cammerer, Annegret H Thieken, Peter H Verburg, 2012 Spatio-temporal dynamics in the flood exposure due to land use changes in the Alpine Lech Valley in Tyrol (Austria) 68, 1243-1270
Gert A Schultz, 1995 Changes on flood characteristics due to land use changes in a river basin
Kebede Bishaw, 2012 Application of GIS and Remote sensing techniques for flood hazard and risk assessment: The case of Dugeda Bora Woreda of Oromiya Regional State, Ethiopia
Luis C Blancas and M Baher El-Hifnawi’s 2014 report emphasizes that promoting competitive and low-carbon transport options is essential for enhancing trade efficiency in Vietnam’s island and coastal waterways The study highlights that sustainable transportation methods can reduce environmental impacts while improving connectivity and economic growth in remote regions By investing in modern, eco-friendly maritime infrastructure, Vietnam can facilitate smoother trade flow, attract investments, and support its national development goals Ultimately, building efficient, low-carbon transport systems in Vietnam’s waterways is vital for fostering sustainable trade and regional integration.
Luu Duy Vu, Nguyen Phuoc Sinh, 2012 Applying WMS model for forecasting flood condition in the downstream Han river, Da Nang city
M Yu, Q Li, G Lu, H Wang, P Li, 2015 Investigation into impacts of land-use changes on floods in the upper Huaihe River basin, China 370, 103-108
This study, authored by Nguyen Hieu Trung, Nguyen Thanh Tuu, Trinh Cong Doan, Lam Van Thinh, Dinh Diep Anh Tuan, and Minh Nguyen in 2014, explores the application of GIS technology to enhance urban water management in Can Tho city, Vietnam It emphasizes how GIS can support adaptive strategies for urban water systems amidst climate change challenges The research is part of the UCCRN Case Study 14.1 within the Second UCCRN Assessment Report on Climate Change and Cities (ARC3.2), highlighting its relevance to sustainable urban planning Conducted through collaboration between CSIRO Land and Water in Australia and Can Tho University’s DRAGON Institute, the study provides valuable insights into integrating GIS tools for improving water resilience in Vietnamese urban environments For more information, visit http://uccrn.org/casestudies/.
Nguyen Thuy Duong (2016) conducted a comprehensive assessment of water quality along Bui River from upstream to Xuan Mai Town, Chuong My, Hanoi, highlighting critical factors affecting river health and proposing effective solutions to enhance water quality Meanwhile, Pham Thi Kim Phung (2011) utilized the HECRAS hydro-physical modeling tool to analyze floodplain delineation in the upstream area of Dak Mi 4, providing valuable insights for flood risk management and sustainable land use planning Both studies contribute significantly to environmental management strategies in their respective regions, emphasizing the importance of integrated water quality improvement and flood control measures.
Tran Van Tinh, 2013 Constructing inundation map in downstream of Vu Gia-Thu Bon basin
Van Khuc, Tien Khanh, 2016 Alarming the situation of dike and floodplain encroachment in Van Uc river
Yuyan C Jordan, Abduwasit Ghulam, Robert B Herrmann, 2012 Floodplain ecosystem response to climate variability and land-cover and land-use change in Lower Missouri River basin 27, 843-857
APPENDIX 1: DATA COLLECTION AFTER FIELDWORK
Width of sub- cross section (m)
APPENDIX 2: DATA OF LAND-USE CHANGE FROM 2005 TO 2014
I II III IV V VI VII VIII IX X XI XII
I II III IV V VI VII VIII IX X XI XII
Total rainfall 2200.3 Amount of rainny days 159
I II III IV V VI VII VIII IX X XI XII
I II III IV V VI VII VIII IX X XI XII
I II III IV V VI VII VIII IX X XI XII
I II III IV V VI VII VIII IX X XI XII
I II III IV V VI VII VIII IX X XI XII
I II III IV V VI VII VIII IX X XI XII
I II IV V VI VII VIII IX X XI XII
I II III IV V VI VII VIII IX X XI XII
I II III IV V VI VII VIII IX X XI XII
I II III IV V VI VII VIII IX X XI XII
Tháng Ngày I II III IV V VI VII VIII IX X XI XII
I II III IV V VI VII VIII IX X XI XII
I II III IV V VI VII VIII IX X XI XII
Tháng Ngày I II III IV V VI VII VIII IX X XI XII
Tháng Ngày I II III IV V VI VII VIII IX X XI XII
Tháng Ngày I II III IV V VI VII VIII IX X XI XII
Tháng Ngày I II III IV V VI VII VIII IX X XI XII
Tháng Ngày I II III IV V VI VII VIII IX X XI XII
Tháng Ngày I II III IV V VI VII VIII IX X XI XII