INTRODUCTION
Introduction
Vietnam has 2360 rivers and canals that have 220000 km in length Only about 19%
Approximately 41,900 km of navigable waterways exist in the country, with 7% (15,436 km) managed for navigation (Luis C Blancas and M Baher El-Hifnawi, 2014) The country’s tropical monsoon climate brings frequent heavy rainfall, making floodplains highly significant Floodplains are zones adjacent to rivers, lakes, ponds, and oceans that periodically flood due to lateral overflow, serving critical hydrological and ecological functions These areas are vital for water storage, conveyance, water quality protection, and groundwater recharge, while also providing essential habitats for fish and wildlife Despite natural flooding along rivers and coastlines, floodplains offer ecological benefits and support biodiversity, making their management crucial.
Land cover change, driven by human demand, significantly impacts floodplains, especially floodplain wetlands of large rivers Anthropogenic activities such as draining, land conversion, and chemical and physical alterations from land and water management practices have detrimental effects on these vital ecosystems (James Kriz et al.).
In 2007, land clearing along river banks became common for activities such as vegetable cultivation and animal husbandry, significantly impacting adjacent river areas Infrastructure development, including bridges and buildings, further alters these ecosystems As population growth increases the demand for land, some communities encroach upon floodplains to meet their needs, often leading to increased environmental pressure and risk of flooding.
Floodplain development poses significant threats to water quality, storage capacity, and natural habitats of aquatic organisms, while also increasing flood hazards Unregulated development in flood-prone areas can lead to severe economic disruptions and loss of human lives, especially in densely populated regions In Vietnam, challenges in floodplain management are compounded by unclear strategies and widespread illegal activities, such as the construction of manufacturing yards within floodplains in Gia Vien district, which narrows rivers and causes traffic congestion during floods Additionally, illegal housing developments like those by Northwest Mineral Corporation in Phu Tho province highlight the disregard for floodplain regulations, emphasizing the urgent need for effective management policies to mitigate flood risks and protect communities.
Bui River is a 91-kilometer-long tributary of the Day River, with a catchment 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 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 has been a lack of studies examining how land use and cover alterations influence Bui River’s hydrological conditions and floodplain dynamics Consequently, this study titled “Floodplain Development in Bui River Due to Land-Use Change from 2004 to 2015” was conducted to address this research gap.
Literature review
1.2.1 Introduction of GIS, HECRAS and HEC-GeoRAS
A Geographic Information System (GIS) is an advanced information system that utilizes spatial data inputs, databases, and outputs related to geography GIS plays a vital role in supporting natural resources planning and management, enabling more efficient urban development and better organization of administrative information By leveraging GIS technologies, urban planners and environmental managers can make informed decisions, optimize resource allocation, and enhance sustainable development efforts.
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 essential information on flood levels and inundation areas Such data plays a critical role in informing citizens about flood risks and helping to mitigate the potential consequences of flooding.
HEC-RAS, developed by the Hydrologic Engineering Center of the U.S Army Corps of Engineers, is a comprehensive hydraulic modeling system designed to simulate the physical properties of streams and rivers This sophisticated software enables detailed routing of flow through natural or artificial water bodies, providing insights into hydrologic characteristics Featuring an intuitive graphical interface along with robust database and data management tools, HEC-RAS allows users to visualize flow dynamics through water depth, inundation areas, and floodplain mapping, making it a vital tool for hydrologic analysis and flood risk assessment.
HEC-GeoRAS is an effective tool that seamlessly integrates GIS data with HEC-RAS within the ArcGIS interface It utilizes inputs such as Digital Elevation Models (DEMs), infrastructure maps, land use, and land cover data to accurately construct inundation maps These maps are essential for analyzing flood extents and calculating the economic impact of flooding events By combining GIS and hydrologic modeling, HEC-GeoRAS provides comprehensive insights for flood risk assessment and management.
1.2.2 Application of GIS, HECRAS and HEC-GeoRAS in modeling floods
Recent advancements in GIS tools and techniques have significantly enhanced their application in river engineering projects Notable 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 utilized GIS to assess how land use changes impact flood characteristics Similarly, Jie Liu, Shao-yu Wang, and Dong-mei Li have contributed to this growing field, demonstrating GIS's vital role in understanding and managing river and flood dynamics.
In 2014, research examined how land-use changes influence flood exposure in Wuhan, situated within the Yangtze River basin Nguyen Hieu Trung also evaluated urban water management strategies utilizing GIS technology Several commercial software packages now integrate GIS with hydraulic modeling for comprehensive spatial analysis, as highlighted by Abolghasem et al in 2014 Notably, the Hydrologic Engineering Center's River Analysis System (HEC-RAS) is a publically available software that interfaces with ArcGIS via HEC-GeoRAS, enhancing flood modeling and analysis 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 to assess changes in floodplain boundaries over 50 years due to land-use modifications Additionally, Karl-Erich Lindenschmidt, Apurba Das, Prabin Rokaya, and Thuan Chu (2015) combined ArcGIS and HEC-GeoRAS to evaluate ice jam flood hazards in the Town of Peach River.
Vietnam currently utilizes various hydrologic models for flood research, including MIKE FLOOD, HEC-RAS, and WMS, each offering unique advantages tailored to researchers' specific needs These models are essential tools for analyzing and predicting flood behavior, aiding in effective flood management and mitigation strategies Notable studies have demonstrated how selecting the appropriate model can improve the accuracy of flood risk assessments and support sustainable urban planning in Vietnam.
Luu Duy Vu and Nguyen Phuoc Sinh (2012) successfully applied the 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, enabling accurate identification of model parameters and validation of the results This study highlights the WMS model's potential as a reliable tool for flood risk assessment and management in urban areas.
- 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 for downstream areas in the Vu Gia – Thu Bon basin, as demonstrated by Tran Van Tinh (2013), represents a significant effort that combines advanced HEC models—HEC-HMS, HEC-RAS, and HEC-GeoRAS—with GIS data.
In 2011, Pham Thi Kim Phung conducted a comprehensive study utilizing the HEC-RAS one-dimensional hydraulic model to delineate floodplains upstream of Dak Mi Her research focused on modeling current flow conditions and predicting various flood scenarios, providing valuable insights into floodplain extent The findings greatly contributed to flood risk assessment, early warning systems, and informed re-planning and mitigation efforts for the Dak Mi upstream region.
- 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 area encompasses the Bui River and its basin, extending from Lam Son commune in Luong Son district, Hoa Binh province, to Xuan Mai town in Chuong My district, Hanoi It covers seven key localities, including Lam Son, Tan Vinh, Nhuan Trach, Hoa Son, Luong Son, Xuan Mai, and Thuy Xuan Tien.
- 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 terrain with low mountains and hills, serving as a transitional zone between the delta and midland regions The area's arable land features a complex, undulating landscape with bumpy fields, which, along with the average elevation of the hills and mountains, provides favorable conditions for the development of forestry and agriculture.
The Bui River Basin experiences a tropical monsoon climate, characterized by distinct seasonal changes influenced by the Northeast, Southeast, and Southwest monsoons From November to March, the Northeast monsoon brings cooler, dry air, while the Southeast monsoon, prevailing from April to July, brings increased humidity and rainfall Additionally, the Southwest monsoon also impacts the region's climate, contributing to the area's seasonal variability This climate pattern significantly shapes the natural resources and ecological conditions of the study area.
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, comprising Luong Son town, Lam Son, and Tan Vinh communes, is rich in mineral resources, including limestone, building stone, clay, basalt, and polymetallic ores Despite this abundance, a significant clay source in Xuan Mai town remains underutilized, primarily used for brick and tile production.
Historically, the natural forests in Tan Vinh, Lam Son communes, and Luong Son town were rich and diverse, featuring many valuable woody species However, extensive artificial disturbances have led to the destruction of large forest areas, replaced by secondary forests Currently, these forests are primarily utilized for production purposes, with only a small portion reserved for protection and special uses In contrast, forests in Xuan Mai town are mainly dedicated to research and study activities.
Located conveniently near Hanoi, this destination offers a perfect blend of natural and cultural attractions Its mountainous terrain and flowing river systems create ideal conditions for ecotourism, resorts, and golf courses Visitors can also explore cultural tourism experiences, such as the Muong cultural village in Tan Vinh commune, enriching their trip with local traditions and heritage.
The Bui River Basin is experiencing rapid population growth driven by its favorable natural conditions The local economy is shifting from agriculture to a growing focus on industrial and service sectors, prompting residents to alter land cover to meet their changing needs Notably, land modification efforts are concentrated near the main flow of the Bui River to support expanding economic activities.
Methods
Secondary data collection is a crucial initial step in developing an accurate computational model for the study area Necessary documents include a land use database covering 2004 to 2016, and a Digital Elevation Model (DEM) of the Bui River basin, obtained from http://gdex.cr.usgs.gov/gdex/ Hydrometeorological data for the Bui River, such as flow discharge and rainfall, were collected at Lam Son station upstream, spanning 2004 to 2015 Rainfall data were recorded daily using a Vietnamese rain gauge, while flow discharge during the same period was calculated by staff at Lam Son station, utilizing cross-sectional measurements 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 equipment including a tape measure, a stopwatch, and a meter stick for measuring depth Additionally, use at least three highly visible buoyant objects, such as oranges, that are buoyant enough to remain unaffected by wind Securely anchor the tape measure to stream banks using stakes, ensuring accurate and reliable measurements during your observations.
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
Vsurface = 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)
Based on collected data, river bed elevation and bathymetry can be accurately determined, along with flow discharge measurements Stream discharge, the volume of water passing a specific point in the river channel over a set period, is primarily influenced by water flow velocity and the cross-sectional area of the stream Understanding these parameters is essential for effective river management and hydrological studies.
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 construct the land use map of the Bui River Basin, comprehensive data from Chuong Mi and Luong Son districts across different periods are essential This data is imported into MapInfo for editing and smoothing to ensure accuracy The land use map is then transferred from MapInfo to ArcGIS using the FME converter The final Bui River Basin land use map is extracted from the district maps through a series of steps, including Arc Toolbox, Spatial Analyst tools, Extraction, and Extract by Mask, ensuring precise delineation of land use patterns.
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 generated using HEC-GeoRAS and then imported into HEC-RAS for detailed hydraulic modeling For a new project named TEST13092016, all existing geometric data—such as stationing, elevations, downstream reach length, Manning's n values, and main channel bank stations—were incorporated and refined to ensure comprehensive analysis Steady Flow Analysis in HECRAS is utilized to compute the water surface profile for steady, gradually varied flows, allowing for accurate modeling of current conditions Additionally, HECRAS simulations of four flood scenarios, by adjusting boundary conditions like normal depth, known water surface, and discharge, provide insights into potential flood impacts based on the principle of positive correlation of water surface profiles along the river.
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 from July 11th, 2006, was used to delineate the flooded areas on 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 the entire floodplain area These cross sections were then assigned water levels to develop a Triangular Irregular Network (TIN) model for accurate flood mapping.
Figure 3.7 Triangular irregular networks (TIN) model of study site
The TIN model effectively captures the surface morphology of floodwaters by representing water surface elevation This model was then interpolated into a raster format, providing water surface elevation values for each pixel By subtracting the flood event's water elevation model from the digital elevation model of the study area, the floodplain was derived, with only positive difference values indicating flood-prone areas along the Bui River These processing steps were consistently applied to generate floodplain maps for other flood events, ensuring accurate and comparable results.
RESULTS AND DISCUSSION
Characteristics of hydrological conditions and land-use/cover change in Bui river
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 nthly ra infa ll (m m )/ m o nth
M o ntly dis cha rg e (m m /m o nth )
The flooding season in the Bui River typically occurs from May to October, with peak runoff volumes recorded in July, August, and September based on discharge data from Lam Son station Throughout the study period, the rainy season accounted for between 58.4% (2008) and 88.5% (2011) of the total annual runoff, highlighting the significant contribution of this period to overall water flow in the river.
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
Runo ff co ef ficient ( %)
An n u a l ra in fa ll ( m m /y ea r)
Annual runoff is closely related to annual rainfall, as described by the equation y = 0.6093x – 42.176, where y represents annual runoff and x denotes annual rainfall The high coefficient of determination, R² = 0.9948, indicates that approximately 99.48% of the variability in annual runoff can be explained by this linear model, highlighting a strong correlation between rainfall and runoff (Figure 4.3).
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
According to the Natural Resources and Environment Departments of Luong Son (Hoa Binh) and Chuong My (Hanoi) districts, land-use maps for 2005, 2010, and 2014 were generated with support from MapInfo These maps reveal that land use in the Bui River basin has been categorized into eight main 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 Land-use change data, measured in hectares, is provided in Appendix 2, with the statistical relationship indicated by the equation y = 0.6093x - 42.176 and a high coefficient of determination, R² = 0.9948, demonstrating a strong correlation.
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, the Bui River basin experienced notable land use changes, including a 9.15% increase in forest land, a 1.38% rise in residential areas, and a 0.77% growth in industrial zones The transportation network was continuously upgraded, with a 0.74% expansion, highlighting its vital role in connecting Hanoi and Hoa Binh Province, which host key industrial zones Additionally, local land use planning led to significant reductions in unused land by 6.55% and agricultural land by 3.62%, reflecting efforts to optimize land resources within the basin.
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 land-use/cover changes in the Bui River basin show significant expansion of large built-up areas with impervious surfaces, especially near the main river channel These impervious areas include residential zones, industrial zones, transportation infrastructure, cemeteries, defense areas, educational institutions, and public service facilities Land-use maps from 2005, 2010, and 2014 reveal that the total impervious area (%TIA) increased from 25.57% to 28.21% and then to 29.59%, indicating a consistent upward trend over the study period This growth highlights the ongoing urbanization and expansion of impervious surfaces within the basin, which may impact watershed hydrology and environmental health.
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 centa g e o f la nd -us e ca teg o 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
The accuracy assessment of floodplain modeling is essential for reliable results This study compared observed widths from ten cross sections measured in the field with simulated widths for the same sections The correlation between observed and simulated widths was represented by the equation y = x, indicating a strong linear relationship The model achieved an R-squared value of 0.8879, demonstrating an accuracy of 88.79%, which underscores its reliability 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 effects of land-use change on floodplain dynamics by analyzing four flood events with similar rainfall inputs The selected flood events all occurred on July 11th, ensuring consistent precipitation conditions for accurate comparison Understanding these events helps to assess how land-use modifications influence flood behavior and floodplain resilience The findings provide valuable insights for flood risk management and sustainable land-use planning.
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 are classified into modification and conversion; modification involves within-type condition changes, such as forests becoming more scattered due to selective thinning, while conversion refers to transforming one land-use type into another, like converting farmland into residential areas In the Bui river basin from 2004 to the present, notable changes include replacing agricultural and unused lands with built-up areas and expanding forest land in upstream regions The impervious surface area, encompassing residential zones, industrial areas, transportation systems, and public facilities, increased from 25.57% to 29.59% between 2005 and 2014, leading to higher surface runoff and reduced infiltration The decline in agricultural land, a primary water source for irrigation, has caused water levels in the main channel to rise, resulting in increased water surface elevation at Lam Son station and floodplain areas despite similar or decreasing rainfall amounts during four flood events.
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
F lo o dpla in a rea (ha)
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
Proximity to water supplies, fertile soils, and flat landscapes contributes to the growing population in floodplains To enhance the resilience of river communities, it is essential to address flood risks through both structural solutions like levees and flood storage, and non-structural measures such as effective flood warning systems and regulatory policies Implementing a combination of these strategies can effectively mitigate flood hazards and protect vulnerable populations.
Effective floodplain management requires a comprehensive long-term action plan that recognizes the vital role of natural floodplain ecosystems Implementing clear strategies to reduce flood risks and enhance water quality is essential for sustainable floodplain conservation For example, restoring natural floodplain functions and adopting sustainable land use practices can significantly decrease flood occurrence and improve water health.
- 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 building and construction, effectively increases surface permeability within river basins This approach reduces the land's water retention capacity over large areas, helping to improve water runoff and manage flood risks Using permeable materials in infrastructure promotes sustainable water management and mitigates urban flooding, making it a vital strategy for conserving natural water flow within river basins.
- 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 knowledge exchange among scientists, public officials, and industry representatives, stakeholders become more informed about sustainable floodplain management This collaborative approach is essential for preventing encroachment actions that threaten the integrity of floodplains Implementing effective floodplain management strategies helps protect these vital ecosystems from future threats and ensures their long-term resilience.
Evaluation of the interactions between changes in land-use/cover, hydrological
This study evaluates the impact of land-use change on floodplain dynamics by analyzing four flood events characterized by similar rainfall amounts The selected events all occurred on July 11th, ensuring consistency in rainfall conditions By focusing on these equivalent flood events, the research provides accurate insights into how land-use modifications influence flood behavior and floodplain processes These findings are essential for developing effective flood management and land-use planning strategies.
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 are classified into modification and conversion, where modification involves within-type condition changes, such as forests becoming more scattered through selective thinning, while conversion refers to transforming one land-use type into another, like turning farmland into residential areas In the Bui river basin from 2004 to the present, significant land-use changes include the replacement of agricultural and unused lands with built-up areas and the expansion of upstream forest land The impervious surface area, encompassing residential, industrial, transportation, and public service zones, increased from 25.57% to 29.59% between 2005 and 2014, leading to enhanced surface runoff and reduced infiltration The reduction in agricultural land, a primary source of stream water for irrigation, has caused water levels in the main channel to rise Despite nearly stable or decreasing rainfall during four flood events, water surface elevation in Lam Son station and floodplain areas increased due to these land-use changes.
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
F lo o dpla in a rea (ha)
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
The increasing population in floodplains is driven by proximity to water supplies, fertile soils, and flat landscapes 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 regulatory policies Implementing these integrated strategies can significantly mitigate flood hazards and protect vulnerable communities.
Developing a long-term floodplain management plan requires a thorough understanding of the ecological benefits of natural floodplain ecosystems Effective strategies should focus on reducing the risk of flood events while enhancing water quality Implementing these approaches helps to sustainably manage flood risks and preserve vital natural habitats.
- 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 the use of partial permeable materials in construction, enhances surface permeability in river basins This approach reduces water retention over large areas, promoting improved water flow and minimizing flood risks Utilizing permeable materials for building and infrastructure development offers a sustainable solution to manage water drainage efficiently and protect river ecosystems.
- 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
Knowledge exchange among scientists, public officials, and industry representatives is essential for promoting sustainable floodplain management This collaborative approach raises awareness of effective strategies to prevent encroachment, which can threaten the long-term health of floodplains Implementing sustainable floodplain management is a crucial solution to reduce environmental risks and protect these vital ecosystems for future generations.
CONCLUSION AND RECOMMENDATIONS
Conclusion
This study concludes that the flow regime of Bui River exhibits two distinct 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) Land-use changes in the Bui River basin indicate an increasing trend in impervious surfaces, rising from 25.57% to 29.59%, while agricultural and unused lands decreased by 3.62% and 5.55%, respectively Despite consistent rainfall amounts, increases in river width and water surface elevation were observed, highlighting the impact of land development A notable relationship exists between impervious area percentage and floodplain area, modeled by y = 4.9064x + 10.47 (R² = 0.97), emphasizing that floodplain development is primarily influenced by land-use changes and infiltration processes To promote sustainable development, the study recommends strategies such as enhancing community resilience, implementing ecohydrology planning, raising public awareness, and facilitating knowledge exchange to improve corridor management.
Recommendations
This study successfully applies the 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 my knowledge and skills have impacted the accuracy of the results To enhance future research, collecting more comprehensive land-use planning data, increasing the number of cross sections along the river, and improving technical skills in using advanced hydrological modeling tools are essential.
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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) demonstrates how GIS and remote sensing techniques can effectively assess the impact of land use changes on flood hydrology in the Yialias basin, Cyprus The research highlights the importance of spatial analysis tools in identifying land use dynamics and their influence on flood events By analyzing satellite imagery and GIS data, the study provides valuable insights into how urbanization and land cover modifications alter flood risk The findings emphasize that integrating GIS and remote sensing is crucial for sustainable land management and flood mitigation strategies Overall, this case study underscores the role of advanced geospatial technologies in enhancing understanding of flood hydrology related to land use changes.
The 2007 open-file report by Kriz, Huggins, Freeman, and Kastens, titled "Assessment of Floodplain Wetlands of the Lower Missouri River Using a Reference-based Study Approach," provides a comprehensive evaluation of floodplain wetland ecosystems along the Lower Missouri River This study, published by the Kansas Biological Survey, utilizes a reference-based methodology to accurately assess wetland health and extent in the region The report emphasizes the importance of floodplain wetlands for biodiversity, flood mitigation, and ecological integrity Key findings highlight the current condition of these wetlands and recommend strategies for conservation and sustainable management to protect their ecological functions.
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
This report highlights the potential of Vietnam’s island and coastal waterways to facilitate trade through the development of competitive, low-carbon transportation solutions It emphasizes that investing in sustainable transport infrastructure can improve connectivity, boost economic growth, and reduce environmental impacts The study underscores the importance of modernizing maritime and inland waterway systems to enhance trade efficiency while promoting environmentally friendly practices By leveraging Vietnam’s unique geographical advantages, the report advocates for policies that support low-carbon transport options, ultimately contributing to the country’s sustainable development goals.
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
Nguyen Hieu Trung, Nguyen Thanh Tuu, Trinh Cong Doan, Lam Van Thinh, Dinh Diep Anh Tuan, and Minh Nguyen (2014) conducted a case study on applying GIS technology to enhance urban water management in Can Tho City, Vietnam, amidst climate change challenges Their research, titled "Application of GIS to Support Urban Water Management in Adapting to a Changing Climate," is documented as Report UCCRN Case Study 14.1 in The Second UCCRN Assessment Report on Climate Change and Cities (ARC3.2) The study highlights how GIS tools can improve resource allocation, infrastructure planning, and resilience strategies for urban water systems This research was a collaborative effort between CSIRO Land and Water in Australia and the DRAGON Institute at Can Tho University, Vietnam, providing valuable insights into sustainable urban water management in the face of climate variability.
Nguyen Thuy Duong (2016) conducted a comprehensive assessment of water quality along the Bui River from upstream to Xuan Mai Town in Chuong My District, Hanoi, highlighting key factors affecting river health and proposing practical solutions to improve water quality Meanwhile, Pham Thi Kim Phung (2011) applied the HECRAS model to delineate floodplains in the upstream area of Dak Mi 4, providing valuable insights for flood management and land-use planning Both studies emphasize the importance of integrated environmental and hydraulic analysis to promote sustainable river and floodplain management in Vietnam.
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