River Channel Morphology Research Articles

Spatial Variability in Bankfull Stage and Bank Elevations of Lowland Meandering Rivers: Relation to Rating Curves and Channel Planform Characteristics

AbstractMutual adjustment between process and form shapes the morphology of alluvial river channels, including channel banks. The tops of banks define the transition between the channel and adjacent floodplain, which corresponds to the level of incipient flooding. Despite the geomorphological and hydrological importance of this transition, few, if any, studies have extensively examined spatial variability in bank elevations and its influence on bankfull stage. This study uses an objective method to explore this variability at two spatial resolutions along three alluvial lowland meandering rivers. Results show that variability in bankfull stage is inherent to all three rivers. The mean variability of bankfull stage about the average downstream gradient in this stage is 10% to 20% of mean bankfull depth. Elevations of channel banks exhibit similar variability, even after accounting for systematic variations in heights of inner and outer banks associated with river meandering. Two‐dimensional hydraulic simulations show that the elevation range of mean variability in bankfull stage overlaps considerably with the elevation range of high curvature on rating curves, confirming that variability in bankfull stage influences the shape of these curves. The simulations verify that breaks in channel banks allow flow to extend onto the floodplain at stages below the average bankfull stage. The findings provide fundamental insight into the variable nature of bankfull conditions along meandering rivers and the role of this variability in channel‐floodplain connectivity. The results also inform river‐restoration efforts that seek to re‐establish the natural configuration of channel banks.

Erosion, Sediments Transport and Riverbank Stability: A Review

This paper is a review of the basic theoretical information needed to understand the riverbank stability, failure mechanism, and its causes. The first part describes the basic principles of river systems involving river hydraulics, sediment load, and channel morphology. This is pursued by a brief discussion concerning riverbank erosion that involves theoretical equations and numerical methods to quantify erosion. Finally, an in-depth discussion concerning riverbank stability that involves the types of failure mechanism, tension cracks, and riverbank settlement is conducted. Also, the paper reviews some previous studies on riverbank stability.

Meriç Nehri Yatak İçi Kum Alımının Jeomorfolojik Değerlendirmesi

In-channel sand excavation has been implemented on the River Meriç flowing through Turkey for the last 15 years to prevent or mitigate floods and to generate income. Sand removal was carried out by digging in-riverbed sand deposits in the 12 km section of the river running alongside the city of Edirne. This study aimed to investigate the geomorphological effects of in-channel sand excavation on the River Meriç in the Edirne province and to evaluate the results. The 12 km section of the River Meriç in the Edirne province was examined between 2008 and 2019. The braided channel pattern of this part of the river was mapped for a one-year period. Annual variation characteristics were determined using GIS and RS. Flow observations and change characteristics in the river channel morphology were then correlated. Changing the natural river channel form and channel cross-sectional characteristics of the river has led to changes in river erosion and deposition. It is predicted that these changes will play a triggering role in causing unexpected fluvial geomorphology problems. We suggest that the expected economic input for river sand mining should be re-evaluated from the perspective of cost-benefit analysis.

Three-dimensional hydrodynamic modeling of the Santos-São Vicente-Bertioga estuarine system, Brazil

Composed of three channels, a bay and an extensive mangrove area, the Santos-São Vicente-Bertioga estuarine complex, which is located in São Paulo, Brazil, is one of the most important water resources for the region. It hosts the activities of the largest Brazilian port and is used for recreational and subsistence activities. Due to its complexity and different forms of use, the study of its hydrodynamics is of extreme importance and an ongoing concern for researchers and decision makers. Generally, hydrodynamic studies are performed through field monitoring, which is a limited approach because it is discrete in space and time. In view of these limitations, it is necessary to apply field data in conjunction with other tools that allow the integrated assessment of the environment; one of these tools is numerical modeling. Based on this background, this paper presents a hydrodynamic study of the estuarine complex through the application of three-dimensional numerical modeling. Our objective was to improve the representativeness of water level and currents in the water column through time and space, thereby building a background model for future studies involving the understanding of the water circulation in the system. The modeling results showed a high degree of agreement with the in situ measurements. Concerning the water circulation of the complex, the results indicated that the three channels that make up the complex had distinct behaviors; flood currents were dominant in the Santos channel, while ebb currents were dominant in the São Vicente and Bertioga channels. The strongest currents were observed in the Santos channel. We also show that the influence of river discharge and channel morphology creates subregions with different hydrodynamic behaviors within the same estuarine channel.

Controls on channel deposits of highly variable rivers: Comparing hydrology and event deposits in the Burdekin River, Australia

AbstractDischarge event frequency, magnitude and duration all control river channel morphology and sedimentary architecture. Uncertainty persists as to whether alluvial deposits in the rock record are a time‐averaged amalgam from all discharge events, or a biased record of larger events. This paper investigates the controls on channel deposit character and subsurface stratigraphic architecture in a river with seasonal discharge and very high inter‐annual variability, the Burdekin River of north‐east Australia. In such rivers, most sediment movement is restricted to a few days each year and at other times little sediment moves. However, the maximum discharge magnitude does not directly correlate with the amount of morphological change and some big events do not produce large deposits. The Burdekin channel deposits consist of five main depositional elements: (i) unit bars; (ii) vegetation‐generated bars; (iii) gravel sheets and lags; (iv) antidune trains; and (v) sand sheets. The proportions of each depositional element preserved in the deposits depend on the history of successive large discharge events, their duration and the rate at which they wane. Events with similar peak magnitude but different rate of decline preserve different event deposits. The high intra‐annual and inter‐annual discharge variability and rapid rate of stage change make it likely that small to moderate‐scale bed morphology will be in disequilibrium with flow conditions most of the time. Consequently, dune and unit bar size and cross‐bed set thickness are not good indicators of event or channel size. Antidunes may be more useful as indicators of flow conditions at the time they formed. Rivers with very high coefficient of variance of maximum discharge, such as the Burdekin, form distinctive channel sediment bodies. However, the component parts are such that, if they are examined in isolation, they could lead to misleading interpretation of the nature of the depositional environment if conventional interpretations are used.

Integrated assessment of contemporary hydro-geomorphologic evolution of the Indus River Estuary, Pakistan in context to regulated fluvial regimes

The riverine ecosystem is dependent upon the supply of fresh water but the decrease in flows weakens this connection. It gradually leads to impairment of ecologic as well as geomorphologic settings of a riverine ecosystem. Keeping this in view, the present study was designed to assess the contemporary evolution of the Indus River Estuary (IRE) under forced hydrological conditions. An account of transitions in the eco-geomorphologic response of the IRE was synthesized using satellite imageries from 1972 to 2016 and interpreted with the ground observations. Due to flow regulations, an 80% decrease in average annual flow and 50% dampening of flood peaks have altered its hydrological regime. These pronounced hydrological shifts have also played a significant role in the modulation of channel morphology.Similarly, the morphological configuration of the estuary like the length and width of the channel have also increased by 11% and 29%, respectively, and the rate of erosion was more than the deposition. After experiencing significant variations in the rate of lateral migration, the channel has started creeping in a south-eastern direction dominantly since 1993, with an average rate of migration of 44 m/yr. Correspondingly, the riparian landscape has also evolved coherently with a notable competition between bare land and the vegetative cover. Trade-offs between the river hydrology, channel morphology and landscape ecology were understood with a correlation matrix and interpreted with plausible causes. It would help the policymakers to assess the overall ecological health of the IRE and contribute the experts working on designing a framework for the study of system dynamics.

Multimodelling approach to the assessment of climate change impacts on hydrology and river morphology in the Chindwin River Basin, Myanmar

In the tropical region, climate change significantly affects the morphology of river channels as well as water resources. In this study, the climate change impact on hydrology and morphology is assessed in the Chindwin River Basin, Myanmar. Future climate data was developed by an ensemble of four Regional Climate Models (RCMs) using a performance-based weight method, under two Representative Concentration Pathways (RCP4.5 and RCP8.5). Two models were developed: a hydrological model (MIKE NAM) to simulate future discharge and a morphology model (MIKE 21 Flow Model) to simulate morphological changes under climate change scenarios. The results reveal that the mean annual discharge over the period from 2018 to 2040 (23 years) is projected to increase by 13.9 and 22.8%, under RCPs 4.5 and 8.5, respectively. The annual hydrograph shows a sharp rise and the recession of monsoon flood, with multiple peaks replacing the single peak observed during the baseline period (1975–2005) with a delay in peak of 8–10 days. The extreme events (floods) are expected to get more severe in the future in terms of frequency and magnitude compared to the baseline period. The study further shows that under extreme rainfall events, the left bank of the upstream areas is projected to experience severe morphological changes, accompanied by severe flood damage. As high flows become amplified due to climate change in the near future, morphological changes will exacerbate in the same period. Sediment deposition will increase the flood risk and river bank instability, constraining navigability in the river and adversely affecting riverine communities. The study reveals that mathematical modelling helps to identify the impacts of climate change on hydrology and morphology, and that knowledge coupled with an assessment of the vulnerability associated with lives and livelihoods, could help planners and policymakers to develop adaptation strategies and take meaningful action to mitigate the impact.

Морфодинамика и гидроморфология речных русел как разделы учения о русловых процессах

The article considers the structure of the study of channel processes (channel studies) as an independent section of river hydrology, which explores the effect of river runoff on the land surface. The main components of channel studies are the morphodynamics and hydromorphology of the channels. These sections are interacting with the dynamics of the channel flows and the theory of river drifts which depending on the content of the research are part of the channel science or the branches of knowledge unrelated to it. The basis of morphodynamics is the study of the morphology and dynamics of river channels, their technogenic changes, as well as river floodplains as derivatives of channel deformations, and the development of longitudinal river profiles. Hydromorphology develops hydrologic-morphological, hydromorphometric, morphometric and hydrologic-morphodynamic relations, establishes dependencies connecting the parameters of the channels among themselves, and with the hydrological and hydraulic characteristics of the rivers. It is shown that these dependencies are the basis for the development of forecasts of channel deformations as a result of the selfdevelopment of channel forms, natural and anthropogenically caused changes in the natural environment and climate. The methodology of managing channel processes and ensuring hydro-ecological safety during the development of river resources are based on regularities of channel deformations and forecasts of their development.

An Integrated Approach for Constraining Depositional Zones in a Tide-Influenced River: Insights from the Gorai River, Southwest Bangladesh

The tidal to fluvial transition (TFT) of estuaries and coastal rivers is one of the most complex environments on Earth with respect to the transportation and deposition of sediment, owing in large part to competing fluvial and marine processes. While there have been recent advances in the stratigraphic understanding of the TFT, it is still unclear whether these findings are site-specific or representative of mixed tidal-fluvial systems worldwide. Yet, research from this depositional domain holds profound societal and economic importance. For instance, understanding the underlying stratigraphic architecture of channel margins is critical for assessing geomorphic change for fluvio-deltaic settings, which are generally vulnerable to lateral channel migration and resultant erosion. Findings would also benefit paleo-geographic reconstructions of ancient tide-influenced successions and provide an analog for hydrocarbon reservoir models. In the Ganges-Brahmaputra Delta of Bangladesh, the Gorai River is one of two Ganges distributaries actively connected to the Bay of Bengal. With fluvial input from the Ganges and meso-scale (2–4 m range) tides at the coast, the Gorai exhibits a variety of hydrodynamic regimes across its 350-km reach, providing a unique opportunity to investigate along-channel depositional patterns across the TFT. This study integrates multiple datasets—core sedimentology, river channel bathymetry, and remote sensing—to provide a process-based framework for determining the relative position of sedimentary deposits within the tidal-fluvial continuum of the Gorai River. The results of this investigation reveal coincident, abrupt shifts in river channel morphology and sediment character, suggesting the occurrence of backwater-induced mass extraction of relatively coarse sediments (i.e., fine sand). Despite being situated in an energetic tidal environment, evidence of tidal cyclicity in cored sediments is relatively rare, and the bulk stratigraphy appears strongly overprinted by irregularly spaced cm- to dm-scale sediment packages, likely derived from monsoonal flood pulses. Such findings differ from previously-studied mixed tidal-fluvial systems and underscore the site-specific complexities associated with this depositional domain.

Dynamics of loose granular flow and its subsequent deposition in a narrow mountainous river

A large amount of loose debris materials were deposited on the slope of mountainous areas after the 2008 Ms 8.0 Wenchuan earthquake. During and after the earthquake, these loose debris deposits collapsed and slide into valleys or rivers, changing river sediment supply condition and channel morphology. To investigate the mechanisms of granular flow and deposition, the dynamics of slope failure and sediment transportation in typical mountainous rivers of different intersection angles were analyzed with a coupling model of Computational Fluid Dynamics and Discrete Element Method (CFD-DEM). The numerical results show that the change of intersection angle between the granular flow flume and the river channel can affect the deposit geometry and the fluid flow field significantly. As the intersection angle increases, the granular velocity perpendicular to the river channel increases, while the granular velocity parallel to the river channel decreases gradually. Compared to the test of dry granular flow, the CFD-DEM coupling tests show much higher granular velocity and larger volume of sediments entrained in the river. Due to the river flow, particles located at the edge of the deposition will move downstream gradually and the main section of sediments deposition moves from the center to the edge of the river channel. As a result, sediment supply in the downstream river will distribute unevenly. Under the erosion of fluid flow, the proportion of fine particles increases, while the proportion of coarse particles decreases gradually in the sediment deposition. The build-up of accumulated sediment mass will cause a significant increase in water level in the river channel, thus creating serious flooding hazard in mountainous rivers.

Ecological state of the floodplain-channel complexes of small rivers in Novosibirsk

The relevance of this study is due to the increasing man-made stress on water bodies and the land resources connected with them within the urbanized territories, as a result, changes in the morphology and dynamics of river channels and floodplain. It leads to the need for an integrated environmental assessment of floodplain-riverbed complexes, especially small rivers within urbanized areas. The purpose of the study is an integrated environmental assessment of floodplain-channel complexes of small rivers in the city of Novosibirsk to substantiate the recommendations of engineering measures to reduce environmental tensions. The research results showed that the Yeltsovka and the Plyushchikha rivers belong to the group with weak environmental intensity, the Tula, the Yeltsovka-2, the Kamenka, the Kamyshenka are of medium environmental intensity, the Yeltsovka-1 is with strong environmental tension. Significance of the study is that the integral assessment of the floodplain-channel complex of small rivers in the city of Novosibirsk can be used to substantiate the recommendations of engineering measures to reduce environmental tensions, which should be selected based on the obtained integral points, as well as to prevent accidents at various facilities or communications during engineering construction or water engineering design, construction and operation.

Evaluation of the equilibrium of the River Nile morphological changes throughout “Assuit-Delta Barrages” reach

When river channel morphology is changed under dynamic hydrologic conditions, the river re-adjusts itself in terms of dimension, profile and pattern to recover its former equilibrium. In general, a river always tends to experience a state of equilibrium through a process of erosion and deposition. Erosion at one location is almost balanced by deposition at another. The present study aims to evaluate the dynamic morphological equilibrium status of the River Nile over a specific period of time, in terms of riverbed and plan form. To achieve this purpose, Reach (4) of the river between Assuit and Delta Barrages throughout the period between 1982 and 2004 was selected as a case study. Two sets of 296 cross sections (x-secs) of 1982 and 2004 representing the reach were obtained. Also, 3 discharge values of 1982 (low, medium, and high) and their corresponding water surface profiles (WSPs) were collected. The study used the volumetric approach in comparing the aggradation/degradation volumes. X-sec water areas and top widths were computed and compared for the same x-secs of 1982 and 2004 under the 3 WSPs. Then, the volumes of sediment deposition/erosion along the river were computed by the summation of the computed water area difference (WAD) at each x-sec (+ve WAD means deposition & −ve WAD means erosion) considering the third dimension (i.e. length) equal to unity. Also, the plan form changes at each x-sec (top width difference) between the two comparison years were computed. The final comparison results showed satisfactory equilibrium rates, especially during the release of low discharge, where the equilibrium percentage (EP) was 95% and 92.2% with respect to both riverbed and plan form changes, respectively with an average EP = 93.6%. As for the medium discharge, the EP achieved 100% and 74%, respectively (Average EP = 87%). For the high discharge, the EP was 80% and 67%, respectively (Average EP = 73.5%). Finally, it was concluded that the more the discharge released, the less the average EP. Also, the study concluded that the equilibrium status of a river reach depends on the released discharges as every case reveals a different status of equilibrium depending on the inclusion or exclusion of the adjacent floodplain areas. In short, the floodplain areas that come under water due to discharge fluctuations turned out to have an essential impact on the evaluation of river equilibrium status.

Bridge construction and river channel morphology—A comprehensive study of flow behavior and sediment size alteration of the River Chel, India

Human has always modified its surroundings for better adaptation which include the building of urban landscapes, dams, and engineering constructions like bridges and other infrastructures. It has been unveiled from the study of River Chel that when the rail bridge was constructed before 1913, the natural width of the river was nevertheless maintained but the problem was initiated and after the road bridge construction in 1970s when the river width was minimized,the morphological changes started in a large scale. Such modifications have affected nature as well as human communities both positively and negatively. This paper will try to portray the evolution of channel shifting and changes of sediment size regime that the River Chel is experiencing due to the construction of bridges across the middle part of its course. So, this study is concerned about the changes in channel pathway since last 100 years and field-based hydrological parameters and sediment size analysis reveals some distinct changes in the channel planform with alteration of sediment size regime. Simulation of the hydraulic modeling in HEC-RAS specifies the probable affected area with bridges and without bridges in both upstream and downstream of the river course. Hence, the study unveils the alteration of the river hydrology and sediment size caused due to anthropogenic effects and impact of such flow analysis has been evaluated through the bridge scour calculation by CUS method. The discussion concludes that the Odlabari road bridge construction (after 1970) has modified the normal hydrological behavior of the river with a higher probability of bank erosion in downstream and floods in upstream resulting river bottleneck condition.

Climatic control of Mississippi River flood hazard amplified by river engineering.

Over the past century, many of the world's major rivers have been modified for the purposes of flood mitigation, power generation and commercial navigation. Engineering modifications to the Mississippi River system have altered the river's sediment levels and channel morphology, but the influence of these modifications on flood hazard is debated. Detecting and attributing changes in river discharge is challenging because instrumental streamflow records are often too short to evaluate the range of natural hydrological variability before the establishment of flood mitigation infrastructure. Here we show that multi-decadal trends of flood hazard on the lower Mississippi River are strongly modulated by dynamical modes of climate variability, particularly the El Niño-Southern Oscillation and the Atlantic Multidecadal Oscillation, but that the artificial channelization (confinement to a straightened channel) has greatly amplified flood magnitudes over the past century. Our results, based on a multi-proxy reconstruction of flood frequency and magnitude spanning the past 500 years, reveal that the magnitude of the 100-year flood (a flood with a 1 per cent chance of being exceeded in any year) has increased by 20 per cent over those five centuries, with about 75 per cent of this increase attributed to river engineering. We conclude that the interaction of human alterations to the Mississippi River system with dynamical modes of climate variability has elevated the current flood hazard to levels that are unprecedented within the past five centuries.

Springtime Flood Risk Reduction in Rural Arctic: A Comparative Study of Interior Alaska, United States and Central Yakutia, Russia

Every spring, riverine communities throughout the Arctic face flood risk. As the river ice begins to thaw and break up, ice jams—accumulation of chunks and sheets of ice in the river channel, force melt water and ice floes to back up for dozens of kilometers and flood vulnerable communities upstream. Via a comparative analysis between two flood-prone communities in Alaska and Yakutia (Siberia), this study examines key components of flood risk—hazards, exposure, and vulnerability, and existing practices in flood risk reduction in rural Arctic. The research sites are two rural communities—Galena (Yukon River) and Edeytsy (Lena River), which sustained major ice-jam floods in May 2013. The data was acquired through a combination of direct observations on site, review of documents and archives, focus group discussions, and surveys. Five focus groups with US and Russian representatives from disaster management agencies revealed a few similar patterns as well as significant differences in flood risk reduction strategies. The main differences included higher reliance on mechanical and short-term ice jam and flood mitigation efforts (e.g., ice-jam demolition) in the Russian Arctic, and lack of a centralized flood management model in the US. Surveys conducted among population at risk during the site visits to Edeytsy (November 2015) and Galena (March 2016) revealed higher satisfaction levels with the existing flood risk reduction efforts among Edeytsy residents. Survey respondents in Galena indicated the lack of ice jam removal and other flood prevention measures as the key drawback in the existing flood management. Historical analysis, conducted via the disaster Pressure and Release (PAR) model, revealed that springtime flood risk in both regions results from complex interactions among a series of natural processes that generate conditions of hazard, and human actions that generate conditions of communities’ exposure and vulnerability. The analysis revealed colonial heritage, top-down governance, and limited inclusion of local communities in the decision-making as the driving forces of vulnerability in both regions. Seasonal weather patterns and regional river channel morphology determine the location, severity, and duration of floods. The analysis also revealed the importance of continuous communication between all stakeholders in timely and effective flood risk management in both regions.

Landslide-driven drainage divide migration

Research Article| February 23, 2018 Landslide-driven drainage divide migration Maxwell P. Dahlquist; Maxwell P. Dahlquist 1Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA Search for other works by this author on: GSW Google Scholar A. Joshua West; A. Joshua West 1Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA Search for other works by this author on: GSW Google Scholar Gen Li Gen Li 1Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Maxwell P. Dahlquist 1Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA A. Joshua West 1Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA Gen Li 1Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA Publisher: Geological Society of America Received: 19 May 2017 Revision Received: 20 Nov 2017 Accepted: 05 Feb 2018 First Online: 23 Feb 2018 Online Issn: 1943-2682 Print Issn: 0091-7613 © 2018 Geological Society of America Geology (2018) 46 (5): 403–406. https://doi.org/10.1130/G39916.1 Article history Received: 19 May 2017 Revision Received: 20 Nov 2017 Accepted: 05 Feb 2018 First Online: 23 Feb 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Maxwell P. Dahlquist, A. Joshua West, Gen Li; Landslide-driven drainage divide migration. Geology 2018;; 46 (5): 403–406. doi: https://doi.org/10.1130/G39916.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Drainage divide migration reorganizes river basins, redistributing erosive energy and contributing to feedbacks between tectonics, erosion, and climate. However, the conditions governing divide migration and the time scales on which it occurs are poorly understood. By connecting channels to hillslopes in steep landscapes, landslides are expected to play a central role in divide migration and landscape evolution. In this study, we examine landslides triggered by three events (two earthquakes and a tropical cyclone), seeking insight into controls on divide migration. Of the ∼100,000 landslides triggered, we mapped 365 that caused a divide to migrate, resulting in a total exchange of ∼2 km2 between basins from ∼82,000 km2 affected by landsliding. By applying several proposed metrics for divide stability based on river channel morphology, we use our database of divide migrations to test for the role of landslides in coupling between channels and divides. We find that, at the time scale of a single landslide-generating event, patterns of area gain and loss between basins are consistent with landscapes progressing toward steady state, as inferred from channel metrics. We also propose a metric to quantify divide migration, area exchange, and the contribution of an event toward topographic steady state. Restricting our analysis to the main drainage divide, and using estimates of recurrence interval and the rate of topographic evolution in Taiwan, we calculate that landslides triggered by large typhoons account for a minimum of 12%–15% of southern Taiwan’s progress toward steady state. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Landuse Types within Channel Corridor and River Channel Morphology of River Ona, Ibadan, Nigeria

The importance of river a corridor warrants a well thought out and balanced management approach because it helps in improving or maintaining water quality, protecting wetlands, etc. Hence, this study seeks to identify major landuse types within the River Ona Corridor; examine the impact of these landuse types within the River Ona corridor on its channel morphology and understand the risk being posed by these landuse types. The study is designed by selecting two reaches of six times the average width from each of the four major landuse types that exist along the river corridor. This study revealed that along the downstream section of Eleyele Dam of River Ona, natural forest stabilizes river channel banks, thereby presenting a narrow and shallow width and depth respectively but the widest of all is found at the agricultural zones.

THE BENEFITS OF RIVER INDICATORS TO ASSESS THE ECOLOGICAL STATUS OF IIUM CAMPUS

The concept of sustainable campus has emerged from the social, economic and environmental impacts due to anthropogenic activities around the world. One of the initiatives of sustainable campus is the application of ecological indicators. The indicators provide information about the current condition and early warning on the possible risks of environmental impacts to the campus environment. However, lack of understanding on the values of natural ecosystem in campusand the lack of proper planning has led to the depletion of natural ecosystem. The study seeks to examine river degradation in IIUM campus and to explore the benefits of river indicators towards achieving IIUM as an ecologically sustainable campus. Data were gathered using a qualitative approach involving three methods of data collection namely: (i) document analysis, (ii) semi-structured interview and (iii) site inventory. The finding reveals that the application of river channel morphology indicators is an important basis for physical planning in making a campus ecologically sustainable. Further analysis suggests that the suitable indicators to assess the condition of IIUM River are the river channel morphology indicators such as width, depth, channel pattern and slope ratio. The process of selecting the indicators are carried out based on six criteria of good indicators discussed in this study. The study concluded that the application of river channelmorphology indicators is a critical process in physical planning of a sustainable campus as it contributes in preventing the loss of natural ecosystem and it offers a credible basis for creating a conducive place for campus residents.

THE BENEFITS OF RIVER INDICATORS TO ASSESS THE ECOLOGICAL STATUS OF IIUM CAMPUS

The concept of sustainable campus has emerged from the social, economic and environmental impacts due to anthropogenic activities around the world. One of the initiatives of sustainable campus is the application of ecological indicators. The indicators provide information about the current condition and early warning on the possible risks of environmental impacts to the campus environment. However, lack of understanding on the values of natural ecosystem in campusand the lack of proper planning has led to the depletion of natural ecosystem. The study seeks to examine river degradation in IIUM campus and to explore the benefits of river indicators towards achieving IIUM as an ecologically sustainable campus. Data were gathered using a qualitative approach involving three methods of data collection namely: (i) document analysis, (ii) semi-structured interview and (iii) site inventory. The finding reveals that the application of river channel morphology indicators is an important basis for physical planning in making a campus ecologically sustainable. Further analysis suggests that the suitable indicators to assess the condition of IIUM River are the river channel morphology indicators such as width, depth, channel pattern and slope ratio. The process of selecting the indicators are carried out based on six criteria of good indicators discussed in this study. The study concluded that the application of river channelmorphology indicators is a critical process in physical planning of a sustainable campus as it contributes in preventing the loss of natural ecosystem and it offers a credible basis for creating a conducive place for campus residents.

Stepwise morphological evolution of the active Yellow River (Huanghe) delta lobe (1976–2013): Dominant roles of riverine discharge and sediment grain size

The presently active Yellow River (Huanghe) delta lobe has been formed since 1976 when the river was artificially diverted. The process and driving forces of morphological evolution of the present delta lobe still remain unclear. Here we examined the stepwise morphological evolution of the active Yellow River delta lobe including both the subaerial and the subaqueous components, and illustrated the critical roles of riverine discharge and sediment grain size in dominating the deltaic evolution. The critical sediment loads for maintaining the delta stability were also calculated from water discharge and sediment load measured at station Lijin, the last gauging station approximately 100km upstream from the river mouth. The results indicated that the development of active delta lobe including both subaerial and subaqueous components has experienced four sequential stages. During the first stage (1976–1981) after the channel migration, the unchannelized river flow enhanced deposition within the channel and floodplain between Lijin station and the river mouth. Therefore, the critical sediment supply calculated by the river inputs obtained from station Lijin was the highest. However, the actual sediment load at this stage (0.84 Gt/yr) was more than twice of the critical sediment load (~0.35 Gt/yr) for sustaining the active subaerial area, which favored a rapid seaward progradation of the Yellow River subaerial delta. During the second stage (1981–1996), the engineering-facilitated channelized river flow and the increase in median grain size of suspended sediment delivered to the sea resulted in the critical sediment load for keeping the delta stability deceasing to 0.29 Gt/yr. The active delta lobe still gradually prograded seaward at an accretion rate of 11.9km2/yr at this stage as the annual sediment load at Lijin station was 0.55 Gt/yr. From 1996 to 2002, the critical sediment load further decreased to 0.15 Gt/yr with the sediment grain size increased to 22.5μm; however, the delta suffered net erosion because of the insufficient sediment supply (0.11 Gt/yr). In the most recent stage (2002−2013), the intensive scouring of the lower river channel induced by the dam regulation provided relatively coarser sediment, which effectively reduced the critical sediment load to 0.06 Gt/yr, much lower than the corresponding sediment load at Lijin station (~0.16 Gt/yr). Consequently, the subaerial Yellow River delta transitioned to a slight accretion phase. Overall, the evolution of the active Yellow River delta is highly correlated to riverine water and sediment discharge. The sediment supply for keeping the subaerial delta stability is inconstant and varying with the river channel morphology and sediment grain size. We conclude that the human-impacted riverine sediment discharge and grain-size composition play dominant roles in the stepwise morphological evolution of the active delta lobe.