Introductory Chapter: Current Practice in Fluvial Geomorphology: Research Frontiers, Issues and Challenges

Over the last one and half century, the prime interest area of fluvial geomorphology has meandered from global system and local process [1]. Returning to the discipline’s critical role in regional-to-local scale problem solving [2], fluvial geomorphology has experienced awesome progress in understanding of the trends and patterns of riverine landscape dynamics [3, 4]. However, it is necessary to understand the current research interests of the fluvial geomorphologists amid the global challenges. In this direction, all regular research articles allied to fluvial geomorphology in one of the leading geomorphological journals, Geomorphology (ISSN: 0169-555X), are scrutinized for 2018. Among all the 329 regular articles published in 24 volumes (300–323) during 2018, 112 (34%) are within the discipline of fluvial geomorphology. Afterward, the subject matters of the selected articles are grouped into 10 broad themes (Table 1 and Figure 1). As this review work considers one single globally recognized journal and takes a single year as sample therefore, the result may not necessarily highlight all the current research progresses but obviously could detect the directions in which the subject is developing/inclining. While going through the title and abstracts of the 112 sampled research papers, we have grouped them quite readily into 10 broad themes (Figure 1) which are addressed further in turn by the focal words (Table 1). The theme ‘Fluvial sediment environment’ had the greatest number of papers counting 25 (22%); 20 (18%) fall within ‘Holocene Fluvial Chronology (Historical Channel change, Stratigraphy, Paleo Hydrology)’, 18 (16%) in ‘Modelling fluvial environment and application of advanced techniques’, and 11 (10%) in ‘Anthropogenic Controls’. ‘Fluvial morphology (Processes and forms)’ and ‘fluvial hydraulics’ include 7 (6%) articles each, while 6 (5%) fall under ‘(Neo)tectonics’, and ‘Gully and hill slope erosion’. Apart from these, 5 articles (4%) addressed Riverine ecology and 7 (6%) fall within ‘crosscutting fields’ (i.e. fluvial geomorphology in association with other branches of geomorphology). It is interesting to note that there is no article pertaining to ‘river management and restoration’ which is one of the focal themes in present research frontiers of fluvial geomorphology [5]. In consideration of the popular remark ‘Geomorphology is largely an intellectual child of the Twentieth Century’ [6], the review results show that fluvial geomorphology is continuously refocusing on process and forms and thereby making interface with other disciplines like sedimentology. Moreover, much of the research articles we have revisited for the present assessment are basically geomorphological


Current research direction/inclination in Fluvial Geomorphology
Over the last one and half century, the prime interest area of fluvial geomorphology has meandered from global system and local process [1]. Returning to the discipline's critical role in regional-to-local scale problem solving [2], fluvial geomorphology has experienced awesome progress in understanding of the trends and patterns of riverine landscape dynamics [3,4]. However, it is necessary to understand the current research interests of the fluvial geomorphologists amid the global challenges. In this direction, all regular research articles allied to fluvial geomorphology in one of the leading geomorphological journals, Geomorphology (ISSN: 0169-555X), are scrutinized for 2018. Among all the 329 regular articles published in 24 volumes (300-323) during 2018, 112 (34%) are within the discipline of fluvial geomorphology. Afterward, the subject matters of the selected articles are grouped into 10 broad themes (Table 1 and Figure 1). As this review work considers one single globally recognized journal and takes a single year as sample therefore, the result may not necessarily highlight all the current research progresses but obviously could detect the directions in which the subject is developing/inclining. While going through the title and abstracts of the 112 sampled research papers, we have grouped them quite readily into 10 broad themes ( Figure 1) which are addressed further in turn by the focal words ( Table 1). The theme 'Fluvial sediment environment' had the greatest number of papers counting 25 (22%); 20 (18%) fall within 'Holocene Fluvial Chronology (Historical Channel change, Stratigraphy, Paleo Hydrology)', 18 (16%) in 'Modelling fluvial environment and application of advanced techniques', and 11 (10%) in 'Anthropogenic Controls'. 'Fluvial morphology (Processes and forms)' and 'fluvial hydraulics' include 7 (6%) articles each, while 6 (5%) fall under '(Neo)tectonics', and 'Gully and hill slope erosion'. Apart from these, 5 articles (4%) addressed Riverine ecology and 7 (6%) fall within 'crosscutting fields' (i.e. fluvial geomorphology in association with other branches of geomorphology). It is interesting to note that there is no article pertaining to 'river management and restoration' which is one of the focal themes in present research frontiers of fluvial geomorphology [5].
In consideration of the popular remark 'Geomorphology is largely an intellectual child of the Twentieth Century' [6], the review results show that fluvial geomorphology is continuously refocusing on process and forms and thereby making interface with other disciplines like sedimentology. Moreover, much of the research articles we have revisited for the present assessment are basically geomorphological  (1) Cross-cutting Th10 Fluvio-karst landscape evolution (1), fluvial and wave-driven erosion (1), ice sheet meltwater routing (1), debris-charged flood hazard (1), submarine channel evolution (1), debris flows over low gradient channels (1), river-damming and late-Quaternary rockslides (1) but did not inevitably come within fluvial geomorphology largely due to the opening out of techniques and wider interest of the contemporary practitioners of other fields toward riverine landscape. Therefore, although fluvial research, including the cross-cutting fields, comprised 34% of the current geomorphological research, in the upcoming days via technical advances (modeling and GIS) and data acquisition (e.g. remote sensing), the discipline will serve to initiate new arena of research which will be more interdisciplinary. Optimistically, the discipline fluvial geomorphology is going through renaissance in quest of elucidating the genesis, dynamicity and diversity of fluvial landscape [7].

Current research frontiers, issues and challenges ahead 2.1 Contemporary research questions in Fluvial Geomorphology
At the very beginning of the twenty-first century, fluvial geomorphology has emerged as a new arena of research in multiple dimensions. In this direction, the National Research Council (NRC) [8] has addressed nine obvious confronts in Earth surface process discourse: • What does our planet's past tell us about its future?
• How do geopatterns on Earth's surface arise and what do they tell us about processes?  Table 1.
• How do landscapes influence and record climate and tectonics?
• How does the biogeochemical reactor of the Earth's surface respond to and shape landscapes from local to global scales?
• What are the transport laws that govern the evolution of the Earth's surface?
• How do ecosystems and landscapes coevolve?
• What controls landscape resilience to change?
• How will Earth's surface evolve in the 'anthropocene'?
• How can Earth surface science contribute toward a sustainable Earth surface?
These key research questions may be taken effectively by the Earth scientists for further research.

Current research frontiers in Fluvial Geomorphology
In view of the aforementioned challenges in contemporary Earth surface process discourse, NRC [8] has focused on four major research frontiers, relevant for fluvial geomorphology: • Interacting landscapes and climate Indeed, comprehensive appraisal of a fluvial landscape requires understanding of the landscape form, function and evolution [11]. However, instead of viewing the regional landscape (area/polygonal approach) as a whole, reference site (i.e. place/ location) based studies (location/point approach) are in practice these days [12]. This often results misleading outcomes [13]. Another threat in contemporary research direction is that high-resolution, real-time large remote sensing datasets pertaining to riverine landscape emphasize mastery over techniques and draftsmanship rather than enriching critical interpretation skills. This leads to the question-'What is it we are training geomorphologists to do?' [14] 'Should we value quantitative applications over and above anything else in landscape analysis?' [15,16]. Therefore, in view of the multidisciplinary roots of fluvial geomorphology [17], there is a need to understand the conjectural principles of the geomorphological dynamics of river systems apart from skill development to process and contextualize remotely sensed observation.

Epilogue
The current advances in the arena of fluvial geomorphology in association with other Earth system science disciplines are broadly as a result of the contemporary advances in data acquisition and modeling techniques particularly due to the progress in geophysical data acquisition tools, computer programming, geoinformatics, numerical modeling, computational fluid dynamics, numerical dating, laboratory experimentation, etc. With these aids obviously the future prospect of fluvial geomorphology is very promising. However, there is a need to refocus on the fundamental scientific issues concerning landscape dynamicity and diversity over time and space. Amid the global challenges like climate change and anthropogenic intervention to the natural systems, the emphasis could be laid upon understanding the consequent changes in fluvial systems. Moreover, there is a need to address management and restoration issues with the aim to manage the decaying fluvial environment.