Hydro-geomorphology

Abstract
Details are given herein, of the development of an equation for predicting the longitudinal dispersion coefficient in riverine flows, based on 81 sets of measured data, and obtained from 30 rivers in the USA. This equation relates the dispersion coefficient to the hydraulic and geometric parameters of the flow and has been derived using dimensional and regression analysis, with a high correlation coefficient (i.e. R2=0.84). The formulation has been compared with many other existing empirical equations, frequently used to predict the longitudinal dispersion coefficient in riverine flows, with the comparisons based on four different statistical methods. These statistical comparisons have shown that the new equation appears to be more accurate than the other equations considered. The new dispersion equation was then linearly combined with a similar equation recently proposed by Seo and Cheong (J. Hydraul. Eng. ASCE 124 (1998) 25) and this combined equation was then also analysed using statistical methods. The existing empirical equations used to estimate the longitudinal dispersion coefficient and the new equations proposed in this study were included in the advective dispersion equation to predict the suspended sediment concentrations at three sites in the Humber Estuary sited along the northeast coast of England. The average percentage errors between the predicted- and measured-field data for the proposed new dispersion equations were less than those obtained using the previously documented equations.

Major river valleys (e.g. Ganga, Brahmaputra, Narmada, Godavari, Kosi etc.) of India have remained as cradles of human livelihood and achievements throughout the course of human history. In the same way, contributing with floods the Damodar valley of eastern India is nurturing its civilization in different phases through almost 3,500 year. Documented history of ruinous extreme floods is more than 347 years old (1665 – 2012) in the Damodar River. It is true that when this river is in the extreme phase, none can withstand against its power. Still we are not now fully capable to manage the adamant nature of river particularly in the monsoon period. Simultaneously the uncertain event, e.g. cloud burst, heavy monsoon rainfall and cyclones etc., and resultant flash floods are not forecast accurately. As the catchment of Damodar has good physiographic and hydro-meteorological potentiality of floods, it is imperative to know the current status of flood probability and risk. So here an attempt is made to investigate the temporal variation (i.e. natural phase – without dams and controlled phase – with dams) of annual peak flows understanding the dam induced flood hydrological changes in the Damodar River. Using the quantitative techniques, viz., Flood Potential Index (FPI), Flash Flood Magnitude Index (FFMI) and Flood Frequency Analysis (FFA), the magnitude of flash floods and channel dimensions are analyzed to derive significant explanation and prediction about the flood risk in the lower segment of Damodar River.

This paper introduces a new approach for determining the most likely initiation points for landslides from potential instability mapped using a terrain stability model. This approach identifies the location with critical stability index from a terrain stability model on each downslope path from ridge to valley. Any measure of terrain stability may be used with this approach, which here is illustrated using results from SINMAP, and from simply taking slope as an index of potential instability. The relative density of most likely landslide initiation points within and outside mapped landslide scars provides a way to evaluate the effectiveness of a terrain stability measure, even when mapped landslide scars include run out zones, rather than just initiation locations. This relative density was used to evaluate the utility of high resolution terrain data derived from airborne laser altimetry (LIDAR) for a small basin located in the Northeastern Region of Italy. Digital Terrain Models were derived from the LIDAR data for a range of grid cell sizes (from 2 to 50 m). We found appreciable differences between the density of most likely landslide initiation points within and outside mapped landslides with ratios as large as three or more with the highest ratios for a digital terrain model grid cell size of 10 m. This leads to two conclusions: (1) The relative density from a most likely landslide initiation point approach is useful for quantifying the effectiveness of a terrain stability map when mapped landslides do not or can not differentiate between initiation, runout, and depositional areas; and (2) in this study area, where landslides occurred in complexes that were sometimes more than 100 m wide, a digital terrain model scale of 10 m is optimal. Digital terrain model scales larger than 10 m result in loss of resolution that degrades the results, while for digital terrain model scales smaller than 10 m the physical processes responsible for triggering landslides are obscured by smaller scale terrain variability

Abstract
This paper discusses and compares the spatial accuracy of the QUICK finite difference scheme and the third-order convection, second-order diffusion (TCSD) scheme for the severe case with pure advection only. It is shown that the QUICK scheme is generally second-order accurate in space and that a general explicit finite difference representation of various upwind difference schemes is numerically unstable for the severest transport case. Various modified forms of the implicit TCSD scheme are presented with their numerical stability properties being studied and analysed. These modified schemes have been applied to an idealised one-dimensional test basin for the cases of pure advection and of advection and diffusion using three different initial-boundary conditions, including: (a) a sharp front concentration gradient; (b) a Gaussian concentration distribution; and (c) a plug source. A two-dimensional version of the modified TCSD scheme has also been formulated based upon the standard ADI technique and has been applied to three two-dimensional test cases, including pure advection for a circular column and a Gaussian distribution, and advection with diffusion for a Gaussian distribution. Both uniform and rotational flow fields were used for these two-dimensional tests. The scheme has been shown to be attractive, with details of the comparisons between these modified schemes and other similar higher order schemes together with the corresponding analytical solutions also being included in the paper.

Abstract
Details are given of a numerical model study of the fate and transport of trace metals in estuarine waters, with particular application to the Mersey Estuary, located along the northwest coast of England. A dynamically integrated model was first developed, including a two-dimensional depth-integrated model and a one-dimensional cross-sectional averaged model. This model was then refined to predict the hydrodynamic and sediment and trace metal transport processes in the Mersey Estuary. Details are given of the development of a governing equation of the total trace metal transport, including both dissolved and particulate metals. The model was first calibrated against field data, collected during spring and neap tidal cycles, for water levels, salinity and suspended sediment. The calibrated model was then used to investigate the trace metal transport processes in the Mersey Estuary, with the partition coefficient between the dissolved and adsorbed particulate phases being modelled as a function of salinity. Comparisons were also made between the model predictions and field-measured data along the estuary. Reasonable agreement between the model results and field data has been obtained, indicating that the novel approach to model metal concentration distributions is capable of representing the fate and transport of trace metals in estuarine environments and can be used as computer-based tool for the environment management of estuarine waters.

The next generation of digital elevation data (≤3 m resolution) calls for the development of new algorithms for the objective extraction of geomorphic features, such as channel networks, channel heads, bank geometry, landslide scars, and service roads. In this work, we test the performance of two newly developed algorithms for the extraction of geomorphic features: the wavelet-based extraction methodology developed

Abstract
The two-dimensional steady flow of a coastal flow past a headland has been considered. Results from a numerical model are presented to show the transient and steady state flow structures downstream of the headland, for a range of external parameters. It is demonstrated that the flows are of two types. The first type, which is characterised by low values of the bottom friction parameter (M) and low values of the Froude number (Fr), shows deflection of the incident flow around the cape tip and attachment of the flow to the rear face of the headland. For higher values of M and Fr, separation of the flow occurs at the tip of the headland and an attached eddy is generated downstream. Eddy shedding is not observed. The results show that the size of the attached eddy and the vorticity distribution within it are controlled strongly by the value of M, though the maximum vorticity within the eddy depends only upon the incident flow velocity U and the horizontal dimension L of the obstruction. Evidence of oscillatory behaviour is detected during the transient adjustment phase of flow development, with the period of the oscillations being of the same order as vortex shedding periods for the same geometry.

Abstract
In recent years, there has been a growing concern worldwide about climate change and the corresponding apparent increase in the risk and frequency of flooding and about the implications for a wide range of river basin management issues. This paper describes the United Kingdom government's approach to implementing Catchment Flood Management Plans (CFMPs), which will provide a large-scale strategic planning framework for the integrated management of flood risk to people and the development of the natural environment in a sustainable manner. This unified approach is to be adopted across England and Wales, with a view to establishing a unified framework to study flood management in each major catchment. Following on from this introduction to the U.K. approach to high-level flood management, details are given of a study where better water quality management during flood flow conditions has been shown to require a catchment-wide approach to reducing diffuse source pollution from agricultural regions. This study also shows that without this holistic approach to water management, a major cause of non-compliance with an EU Directive would not have been established for this river basin.

The next generation of digital elevation data (≤ 3m resolution)
calls for the development of new algorithms for the objective extraction of geomorphic features, such as channel networks, channel heads, bank geometry, landslide scars, service roads, etc. In this work, we test the performance of two newly developed algorithms for the extraction of geomorphic
features: the wavelet-based extraction methodology developed by Lashermes et al. [2007] and the GeoNet-nonlinear diffusion and geodesic pathsmethodology proposed by Passalacqua et al. [2010]. The study area is part of the Rio Cordon basin, a headwater alpine catchment located in the Dolomites, a mountainous region in the Eastern Italian Alps. The aim of this work is to compare the capability of the two new algorithms in extracting the channel network, capturing channel heads, relevant channel disruptions corresponding to landslides, and representative channel cross-sections. The extracted
channel networks are also compared to the ones obtained using classical methodologies based on an area threshold and an area-slope threshold. A high resolution Digital Terrain Model (DTM) of 1 m served as the basis for such analysis. The results suggest that, although the wavelet-based methodology performs well in the channel network extraction and is able to detect channel heads and channel disruptions, the local nonlinear filter together with the global geodesic optimization used in GeoNet is more robust and computationally efficient, while achieving better localization and extraction of features,
especially in areas where gentle slopes prevail. We conclude that these new methodologies should be considered as valid alternatives to classical methodologies for channel network extraction from lidar, in addition to offering the potential for calibration-free channel source identification and also extraction of additional features of interest.

In recent years, new remote-sensed technologies, such as airborne and terrestrial laser scanner, have improved the detail and the quality of topographic information, providing topographical high-resolution and high-quality data over larger areas better than other technologies. A new generation of high-resolution (<3 m) digital terrain models (DTMs) is now available for different areas and is widely used by researchers, offering new opportunities for the scientific community. These data call for the development of a new generation of methodologies for an objective extraction of geomorphic features, such as channel heads, channel networks, bank geometry, debris-flow channel, debris-flow deposits, scree slope, landslide and erosion scars, etc. A high-resolution DTM is able to detect the divergence/convergence of areas related to unchannelized/channelized processes with better detail than a coarse DTM. In this work, we tested the performance of new methodologies for an objective extraction of geomorphic features related to shallow landsliding processes (landslide crowns), and bank erosion in a complex mountainous terrain. Giving a procedure that automatically recognizes these geomorphic features can offer a strategic tool to map natural hazard and to ease the planning and the assessment of alpine regions. The methodologies proposed are based on the detection of thresholds derived by the statistical analysis of variability of landform curvature. The study was conducted on an area located in the Eastern Italian Alps, where an accurate field survey on shallow landsliding, erosive channelized processes, and a high-quality set of both terrestrial and airborne laser scanner elevation data is available. The analysis was conducted using a high-resolution DTM and different smoothing factors for landform curvature calculation in order to test the most suitable scale of curvature calculation for the recognition of the selected features. The results revealed that (1) curvature calculation is strongly scaledependent, and an appropriate scale for derivation of the local geometry has to be selected according to the scale of the features to be detected; (2) such approach is useful to automatically detect and highlight the location of shallow slope failures and bank erosion, and it can assist the interpreter/operator to correctly recognize and delineate such phenomena. These results highlight opportunities but also challenges in fully automated methodologies for geomorphic feature extraction and recognition.

The search for the optimal spatial scale for observing landforms to understand physical processes is a fundamental issue in geomorphology. Topographic attributes derived from Digital Terrain Models (DTMs) such as slope, curvature and drainage area provide a basis for topographic analyses. The slope–area relationship has been used to distinguish diffusive (hillslope) from linear (valley) processes, and to infer dominant sediment transport processes. In addition, curvature is also useful in distinguishing the dominant landform process. Recent topographic survey techniques such as LiDAR have permitted detailed topographic analysis by providing high-quality DTMs. This study uses LiDAR-derived DTMs with a spatial scale between 1 and 30 m in order to find the optimal scale for observation of dominant landform processes in a headwater basin in the eastern Italian Alps where shallow landsliding and debris flows are dominant. The analysis considered the scaling regimes of local slope versus drainage area, the spatial distribution of curvature, and field observations of channel head locations. The results indicate that: i) hillslope-to-valley transitions in slope–area diagrams become clearer as the DTM grid size decreases due to the better representation of hillslope morphology, and the topographic signature of valley incision by debris flows and landslides is also best displayed with finer DTMs; ii) regarding the channel head distribution in the slope–area diagrams, the scaling regimes of local slope versus drainage area obtained with grid sizes of 1, 3, and 5 m are more consistent with field data; and iii) the use of thresholds of standard deviation of curvature, particularly at the finest grid size, were proven as a useful and objective methodology for recognizing hollows and related channel heads.

This study uses landform curvature as an approach for channel network extraction. We considered a study area located in the eastern Italian Alps where a high-quality set of LiDAR data was available and where channel heads and related channel network were mapped in the field. In the analysis, we derived 1-m DTMs from different ground LiDAR point densities, and we used different smoothing factors for the landscape curvature calculation in order to test the suitability of the LiDAR point density and the derived curvature maps for the recognition of channel network. This methodology is based on threshold values of the curvature calculated as multiples (1–3 times) of the standard deviation of the curvature. Our analyses suggested that (i) the window size for curvature calculations has to be a function of the size of the features to be detected, (ii) a coarse ground LiDAR point density could be as useful as a finer one for the recognition of main channel network features and (iii) rougher curvature maps are not optimal as they do not explore a sufficient range at which features occur, while smoother curvature maps overcome this problem and are more appropriate for the extraction of surveyed channels.

Slope is one of the most important distinguishing features for channel morphology. Variations in the computation of slope from a digital elevation model can affect a wide range of hydrogeomorphically derived applications. We compare different methods for computing channel slope using LiDAR-derived digital terrain models (DTMs) with varying resolutions. We chose a headwater basin of the Eastern Italian Alps, characterized by a dense ephemeral colluvial network and a main alluvial channel as our study area. The identified alluvial morphologies are characteristic of steep mountain streams, namely, cascades and step pools. Field surveys were carried out along the main channel and in some small tributaries. Results indicate that a single method for slope calculation cannot estimate channel slope at the hydrographic network scale. The differential geometry approach for slope calculation tends to overestimate field-surveyed channel slope values for all the DTM resolutions (1, 2, 5 m). When a trigonometric approach for slope calculation is applied, 2 and 5 m DTM resolutions give more consistent results. Nevertheless, a reliable channel slope can be derived from a DTM with an appropriate resolution by choosing a suitable method only after considering the channel width.

Rivers have a lot of complexity and diversity in different environmental conditions, and various natural and human factors affect rivers and change their hydromorphological conditions. In fact, hydromorphological degradation is one of the most important types and causes of river changes which happens due to human interventions and consequently the adjustment of the river channel. Several methods have been developed to study the hydrogeomorphology of rivers. One of these methods is the morphological quality index, which has been proposed as a new protocol to assess the morphological quality of river flow. The present study aims to classify hydromorphological quality of the Haji-Arab River (which is located in the west of Bouin-Zahra city) by Morphological Quality Index (MQI). In this study, two main phases and three sub-phases are used for each phase and applied to eight spans. Various indicators such as: functionality index, artificiality index and adjustment index have been applied on this river. The results show that the amount of MQI in the studied intervals was between 0.82 to 0.74%. Among these, the maximum value was in the spans of 1,2,3,6 with a score of 0.82, while the minimum value was in the span of 8 with a score of 0.74.  In terms of quality, Haji-Arab River is on a good class and has good conditions. The functionality index in this river was zero, which was the result of non-intervention of human in the river. Therefore, it is suggested to protect Haji-Arab River appropriately by proper management.
Extended Abstract
1-Introduction
Several tools have been developed in Europe and worldwide to assess hydromorphology and the methods for physical habitat assessment are the most common approach. These methods generally consist of surveying, characterisation and classification of physical habitat elements, mainly focusing on in-stream features. River management often focuses on individual span of river networks. However, the character and dynamism of river spans depends not only upon natural processes and human interventions within the span, but also within the catchment, particularly upstream of the span.
The Italian Environment Minister has recently issued the WFD monitoring and classification standards, introducing the Morphological Quality Index (MQI), which is part of IDRAIM, as a new and innovative protocol for stream morphological quality assessment. This study aims to apply Morphological Quality Index (MQI) for the hydromorphological analysis of Haji-Arab River.
2-Materials and Methods
Haji-Arab River is one of the southern rivers of Qazvin plain. The river flows generally from south to north. The total area of Haji-Arab Catchment is 130,657 square kilometers and the length of the study span is 7.45 kilometers. Regarding geological divisions of Iran, this region is part of the Urmia-Bazman magmatic belt of Central Iran. The climate of this area is temperate to warm and dry. The average annual flow rate was 0.62 m3/s and the maximum flow was 152 m3/s.
MQI has two phases and the components of the evaluation method. The first phase of the method is dividing the four steps. In step 1, a basic investigation of geology, geomorphology, climate, and the land use of the whole catchment is carried out. In step 2, lateral confinement is analyzed in more details, and three valley settings are differentiated: confined, partly confined, and laterally unconfined channels. In step 3, stream channels are classified into seven river morphologies (straight, sinuous, meandering, sinuous with alternate bars, wandering, braided, anastomosed). Step 4 considers additional discontinuities to further subdivide the stream spans, including hydrological discontinuities, bed slope, or relevant changes in channel width, alluvial plain width, or bed sediment. The second phase of the method is structure and key components of the evaluation procedure. The three aspects are considered for the assessment of the morphological quality of river spans. These aspects are analyzed in terms of three components: (i) the geomorphological functionality of river processes and forms; (ii) artificiality; and (iii) channel adjustments.
A total score was computed as the sum of scores across all components and aspects. The Morphological Alteration Index (MAI) is first defined as follows:
MAI = Stot/Smax
In which Stot is the sum of the scores, and Smax is the maximum score that could be spaned when all appropriate indicators are in class C. The Morphological Quality Index is then defined as
MQI = 1−MAI
The following classes of morphological quality were defined: (i) high, 0.85≤MQI≤1; (ii) good, 0.7≤MQIb0.85; (iii) moderate, 0.5≤MQIb0.7; (iv) poor, 0.3≤MQIb0.5; (v) bad, 0≤MQIb0.3.
3-Results and Discussion
The Haji-Arab River was divided to eight spans based on investigating morphological quality. Regarding to physiographic units, spans 1, 2 and 3 are located in the low plain unit, and spans 4 to 8 are located in the intermontane plain unit. All spans are partly confined with hillslopes or ancient terraces and confinement degree is between 10 and 90 percentages. All of these spans as partly confined channels were classified based on their planimetric characteristics using sinuosity index and braiding index. Except for span 3 (multi-thread), other spans are single-thread channel.
There are no changes in the continuity of sediment and wood flux in all spans. There is no floodplain or negligible in the spans 1, 2, 4 and 5 but discontinued floodplain in the spans 3, 6, 7 and 8. The valley slope is connected to a considerable part of the river in the spans 1, 2, 4, 5 and 8, but connected to a small part of the river in the span 3 and connected to full part of the river in the spans 6 and 7. Except for span 7, all spans have no bank reiteration. All spans have potentially erodible corridors. Moreover, bed forms are compatible with the slope of the valley in the spans 3, 4, 5 and 8, while they are not compatible with the slope of the valley in the spans 1, 2, 6 and 7.  There are no heterogeneous changes of forms in all spans except for the span 3. There are no active flood plain forms in the all spans except for spans 3 and 5 with secondary channels. In all spans, there is no change of cross sections, no natural bed heterogeneity, and no large woods. Linear expansion of vegetation is less than 33%  in the all spans. They showed low width channel-related vegetation except for spans 6 and 7 with medium width channel-related vegetation.
There is no specific changes  channel-forming discharge and discharge, no structure, no changes in sediment discharge due to human interventions, no crossing structures, no protected banks along the river, no embankment,  no structures along the river, no sediment movement, no wood movement, no vegetation cut by humans in all of spans.
There is a change of channel pattern in the spans of 4, 5, 7 and 8 from braided to meandering pattern, drastic changes in channel width in the spans of 4, 5, 6, 7 and 8, low changes of the base level in the spans of 1, 2, 3, 4 and 6, medium changes of the base level in the spans of 5, 7 and 8.
4-Conclusion
The results show that the amount of MQI in Haji Arab River is between 0.82 to 0.74% and in terms of quality Haji-Arab river is in a good category and has good conditions. The artificiality indicators in this river are zero, which is the result of non-intervention of human in the River. Finally, it is recommended that protection of the Haji-Arab River and its corridors is essential. Other aspects of the hydromorphological conditions of the River, including physical habitat assessment, hydrological regime assessment, and the habitat of the river corridor should be considered in the future studies. It is better to study the impact of the dam under construction upstream on the hydromorphological conditions of the Haji-Arab River in the future.

Abstract
The concept of integrated water management forms the background to a research project carried out in India and Malaysia. The project involves the development of numerical models to improve understanding of processes in mangrove systems, and related socio-economic investigations to analyse the interests and decision-making of stakeholders in mangroves systems. The paper summarises some of the conclusions arising from the research, including the continuing need for improved technical understanding of mangroves and its incorporation in participatory decision-making.

High-resolution topographic data have the potential to differentiate the main morphological features of a landscape. This paper analyses the capability of airborne LiDAR-derived data in the recognition of channel-bed morphology. For the purpose of this study, 0.5 m and 1 m resolution Digital Terrain Models (DTMs) were derived from the last pulse LiDAR data obtained by filtering the vegetation points. The analysis was carried out both at 1-D scale, i.e. along the longitudinal channel profile, and at 2-D scale, taking into account the whole extent of the channel bed. The 1-D approach analyzed the residuals of elevations orthogonal to the regression line drawn along the channel profile and the standard deviation of local slope. The 2-D analysis was based on two roughness indexes, consisting on the local variability of the elevation and slope of the channel bed. The study was conducted in a headwater catchment located in the Eastern Italian Alps. The results suggested a good capability of LiDAR data in the recognition of river morphology giving the potential to distinguish the riffle-pool and step-pool reaches.