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Palaeoflood hydrology has emerged as an important tool to infer quantitative and qualitative aspects of ungauged floods based on their physical evidence. Palaeoflood studies in India have largely been undertaken in the rivers of Peninsular India, western India, Ganga plains and the Himalayas to determine the magnitude and age of extreme floods and their connection to variations in the monsoon intensity. Usually, the alluvial domains are unfavourable for the occurrence and preservation of flood deposits and related discharge estimation. However, the alluvial rivers of western India owing to their semi–confined banks comprising late Pleistocene sediments provide an opportunity for investigating both, the high magnitude flood events as well as average flow conditions. In this synthesis we concisely review the recent palaeohydrological studies in western India in terms of flood magnitude, occurrence of extreme events and its relation to the southwest monsoon variability over various time scales. Based on palaeo–fluvial reconstructions, the sedimentation pattern during late Pleistocene appears to be related to changes in channel gradient and the water surface width rather than to discharge variability. On the other hand, the aggradation in channels during early Holocene was largely controlled by the huge sediment influx and the incision that followed was in response to the increase in the discharge and competence of the river flow. The slackwater records from the bedrock channels have revealed that the large magnitude flood events occurred during wet climate phases during the last two millennia. A clustering of high magnitude events at climatic transitions and arid periods during mid–late Holocene has been surmised. Further the flood associated deposits delimited within Quaternary fluvial landforms and channel morphology are vital as these allow quantification of past flood discharges, velocities and stage levels and thus improve the future flood predictions.

In this paper we identify changes in the Indian Summer Monsoon (ISM) intensity during the late Holocene as revealed by palaeohydrological proxies in the fluvial archives of western India. Proxy indices, including the geomorphological, sedimentological, geochemical and biological evidence along with chronology have been employed to highlight the trend in ISM intensity over the late Holocene. It is inferred that on a longer timescale, the Indian Summer Monsoon weakened during the late Holocene however; short pulses of ameliorated monsoon occurred around 3, 1.6 and 0.3 cal ka BP. Clustering of flood events is seen to occur at 3–2.8, 2.2–1.6, 1.3–1.1 and 0.65–0.2 cal ka BP not necessarily coinciding with strengthening of the ISM. Palaeoflood data with regard to the ISM variability shows that the two most prevalent flood events at 0.5 and 1.7 cal ka BP coincide with the weak monsoon period/climatic transition in this region. The occurrence of high magnitude flood events during weak monsoon periods is also reflected in the modern flood and rainfall data. It is surmised that high magnitude flood events may represent peak monsoon periods however, cannot be singularly considered as indicators for enhanced monsoon conditions in a region. Only a more robust database of palaeohydrological proxies can further validate their implications on the monsoonal changes over western India.

A sediment core from a palaeochannel distributary of the Saraswati River basin in western India was investigated through a multi-proxy study using palynology, phytoliths, sedimentology, geochemistry, magnetic mineralogy and chronology. The site is located at the eastern margin of the Little Rann of Kachchh in the northwestern part of the Gujarat Alluvial Plains. The goal was to reconstruct the paleoclimatic and sea level flucutations spanning from the last deglaciation to the late Holocene in the area. The core records suggest at least four episodes of marginal marine environment between the last deglaciation and the late Holocene. The first phase of sediment deposition under marine influence was observed post LGM. The signatures of coeval dry climatic conditions of Older Dryas and Younger Dryas periods besides warm and humid conditions of Bolling-Allerod period are reflected in the core records. The second phase of rise in sea level occurred between ~11,210 and ~9795 cal yr BP, which falls within the period of high gradient of sea-level rise of western India. The third phase of global sea level rise in the area is at around ~5747 cal yr BP which coincides with a high sea level phase along the west coast of India. The final recurrence of sediments with predominant marine signatures post ~2650 ± 180 cal yr BP until ~1530 ± 350 cal yr BP suggests marine to marginal marine conditions in the area.

Element geochemistry and Sr–Nd isotopes have been used to characterise the palaeoflood sediments at a tributary junction in lower Narmada Valley archiving the Little Ice Age (LIA) and to determine the present day sources for the mainstem and the tributary sediments. The major and trace element concentrations show minor variations in values post 360 Cal yr BP. The 87Sr/86Sr and eNd values of palaeoflood sediments range from 0.7122 to 0.7191 and − 2.89 to + 6.28 respectively. The bed sediments from the mainstem river (Narmada) and its tributary (Karjan) yield 87Sr/86Sr values of 0.72394 and 0.7113 and eNd values of − 7.18 and + 6.09 respectively. Potential sources of palaeoflood sediments have been investigated from Sr and Nd isotope compositions and mixing of the mainstem as well as the tributary sediments is suggested. Pronounced contribution from the Deccan Basalt during the early part of the Little Ice Age is inferred. The more radiogenic Nd values indicate a contribution from the weathering of younger Deccan basalts, especially the Poladpur formations. The control of weathering intensity and mineral sorting is observed in ‘higher than the source rock’ 87Sr/86Sr ratios of the sediments. The major and trace element variations during the last 700 years are not conclusive although, isotopic signatures of the flood sediments help in constraining the flux from the tributaries. Sr and Nd isotopic composition of the palaeoflood sediments can be used to track the monsoon intensity and pattern but their concentrations in a fluvial system remain primarily controlled by mineral sorting processes and mixing of sources.

Long-term data on flooding events are necessary for understanding the flood frequency and magnitude variations, but the available instrumental records span only a few decades. Recently, lake sediment sequences have emerged as a relatively untapped archive for high-magnitude floods over longer timescales. In the present study, multi-proxy data from a lacustrine sequence at Timbi in the Dhadhar river basin were analysed to determine high magnitude floods in this semi-arid region of western India in response to southwest monsoon variability. The results indicate the occurrence of discreet high magnitude flood events and depositional phases corresponding to different climatic conditions during the mid to late Holocene. Three large flash floods between 4830 and 2730 cal yr B.P. (Phase-I) have been identified as coeval with flood events from fluvial archives and correlated to the widespread period of aridity and weak monsoon recorded in the lakes of north western India. A shift in the depositional environment from fluvial to lacustrine occurred around 2730 cal yr B.P. as inferred from an abrupt change in the sediment character and palynofacies caused by high intensity flash floods and high sediment influx. Phase II (2730–1730 cal yr B.P.) was marked by periodic erosion and deposition in the catchment and sediment influx during pulses of higher precipitation as evident in the dominance of Glomus sp. and Alternaria sp., and relatively low values in concentration-related magnetic parameters and S-Ratio. A high magnitude flood event occurred at 1770 cal yr B.P. towards the end of phase II. During phase III (1730–880 cal yr B.P.) the monsoon was enhanced and climate was warmer as suggested by low χfd%, SIRM/χ, S-Ratio, higher Ba/Sr ratio and presence of aquatic palynomorphs. A high percentage of structured Organic Matter (OM), low fungal remains and increased Ba/Sr ratios between 880 and 360 cal yr B.P. indicate higher lake waters and better monsoon condition during phase IV. The phase V (360–0 cal yr B.P.) corresponds to lake level lowering, soil formation and eutrophication. The Timbi lake sediments demonstrate the potential for lakes in semi-arid alluvial plains of western India to preserve proxy flood records providing additional archives for generating long-term datasets. The flood record generated substantiates palaeoflood data from the fluvial archive suggestive of regional-scale southwest monsoon variability. Low frequency-high magnitude floods occurred during arid periods and low magnitude-high frequency events during relatively strengthened monsoon and thus have implication for linking the palaeoflood events to the southwest monsoon intensity in the semi-arid continental regions.

The socio-economic development in Mainland Gujarat has been river centric. The physical environment of these rivers relates to the landscape response to climate change and tectonic forcing. There is a great diversity in the land and water resources of the region; on the one hand, where there is excess run-off in the rivers such as Narmada and Tapi, the population in the Sabarmati basin faces water scarcity. The agricultural growth in these basins has been exceptionally high; however, unplanned irrigation activities have put the surface as well as the groundwater resources under severe stress. The industrial effluents discharged into the main rivers or the tributaries further aggravate these problems. Soil and bank erosion though common are still up to a level where conservation methods can be applied. Thus, the socio-economic relevance of these river basins is very high and a large potential exists to further improve the conditions of water supply, agriculture, soil erosion and pollution. Each geomorphic unit has a unique resource potential, and a scientific evaluation of the potential is necessary for the socio-economic development of the region.

A multi-proxy study on the sediments from lower Narmada valley, western India records large flooding events and high sediment influx linked to southwest monsoon variations during late Holocene. On the basis of proxy data and chronology of preserved sediments, three major environmental perturbations at 1809, 1487, and 1187 cal BP have been identified that corroborate well with the regional fluctuations in southwest monsoon variability. A phase of dominant marine influence (between 2185 and 1809 cal BP) is inferred based on the presence of marine palynomorphs, mangrove pollen, and amorphous organic matter and is coincident with the phase of weak monsoon in the region. A transition from marine marsh environment to a phase of high fluvial influx occurred around 1809 cal BP. The fluvial influence is inferred based on the replacement of amorphous organic matter with structured organic matter, presence of fresh water algae, decrease in the δ13C values and dominance of kaolinite clay. The fluvial regime stabilized between 1487 and 1187 cal BP as recorded in the overbank sediments, palynomorphs, and geochemical indices, and sedimentation occurred under a highly oxidizing and high energy condition with long distance transport of sediments. The later incision of the sediment sequence, which post-dates 1187 cal BP, can be attributed to enhanced precipitation. The response of the lower Narmada valley to short term southwest monsoon fluctuations is manifest in the shifting deposition environments and a major role of terrestrial sediment influx variability is surmised, leading to relative sea level variations in this part of the Indian subcontinent. A temporal and process-based interplay between flooding periods and sediment discharge in river systems and tidal conditions is suggested for the tropical estuarine environments.

An important issue faced while employing Pyroelectric InfraRed (PIR) sensors in an outdoor Wireless Sensor Network (WSN) deployment for intrusion detection, is that the output of the PIR sensor can, as shown in a recent paper, degenerate into a weak and unpredictable signal when the background temperature is close to that of the intruder. The current paper explores the use of an optical camera as a complementary sensing modality in an outdoor WSN deployment to reliably handle such situations. A combination of background-subtraction and the Lucas-Kanade optical-flow algorithms is used to classify between human and animal in an outdoor environment based on video data. The algorithms were developed keeping in mind the need for the camera to act when called upon, as a substitute for the PIR sensor by turning in comparable classification accuracies. All algorithms are implemented on a mote in the case of the PIR sensor array and on an Odroid single-board computer in the case of the optical camera. Three sets of experimental results are presented. The first set shows the optical-camera platform to turn in under supervised learning, high accuracy classification (in excess of 95%) comparable to that of the PIR sensor array. The second set of results correspond to an outdoor WSN deployment over a period of 7 days where similar accuracies are achieved. The final set also corresponds to a single-day outdoor WSN deployment and shows that the optical camera can act as a stand-in for the PIR sensor array when the ambient temperature conditions cause the PIR sensor to perform poorly.

Palaeocompetence analysis and palaeodischarge estimation techniques are applied to a late Pleistocene–early Holocene gravel terrace in the Mahi River Basin, western India. Terrace sedimentology, comprising gravels overlain by sand lithofacies suggests a gradual change in palaeohydrological conditions marking a switch from braided to meandering fluvial styles. The discharge values for the gravel bedforms based on the clast size and the cross bed set thickness are estimated between ∼150–180 m 3 s −1 comparable with the present day observed values albeit with a much higher competence. Results indicate that fluvial aggradation occurred under low discharge conditions with intermittent high discharge events depositing longitudinal gravel bars. The incision of these gravel bars and the formation of terraces can be attributed to the higher discharge regime post 9.2 ka. The study further indicates that whereas the aggradation of the gravel terrace during the early Holocene was controlled by the large sediment influx, the incision that followed was in response to the increase in the discharge and competence of the river flow.

The rivers of western India are monsoon dominated and have been so throughout the late Quaternary. Sediment accumulation in these river basins has been controlled by climatic and tectonic changes over a time span from the Late Pleistocene to the recent. The lithofacies assemblages associated with the various sediment archives in the Narmada basin range from the boulders of the alluvial fans to overbank fines on the alluvial plains. Estimates, based on clast size, of stream power and competence, bed shear stress and discharge reveal that hydrological conditions during the Late Pleistocene (∼90 ka) were comparable to the present day. The size of the transported clasts and the thickness of the accumulated sediment indicate the influence of basin subsidence rather than an increase in discharge. Discharge estimates based on sedimentary structures preserved in the alluvial-plain facies suggest that the channel had a persistent flow, with a low width–depth ratio and large meander wavelength. The hydrological changes during the Holocene are more pronounced where the early Holocene is marked by a high-intensity hydrological regime that induced erosion and incision of the earlier sediments. The mid-Holocene stream channel was less sinuous and had a higher width–depth ratio and a higher meander amplitude in comparison with the present-day channel. Palaeo-fluvial reconstructions based on the sediment archives in the alluvial reach of the river basin are important tools in understanding the long-term hydrological changes and the intricate fluvial architecture preserved in the Narmada River basin ensures scope for detailed studies to identify phases of weak and enhanced hydrological regimes.

In the absence of long-term hydrologic and streamflow records an understanding of river morphology (present and past) can help delineate changes in magnitudes of water and sediment discharges. The relict drainage system of Gujarat alluvial plain provides an opportunity to reconstruct the palaeochannel morphology-related discharge estimations. In this paper, based on the geomorphological evidence and channel geometry, an attempt has been made to reconstruct the palaeohydrological condition in the Shedhi River during the Holocene. A comparison of the present day channel of the Shedhi River with that of its palaeo counterpart reveals that the former was carrying much higher bankfull discharge (∼5500m3 s−1) as compared to the present (∼200m3 s−1). This is attributed to a larger drainage area and enhanced precipitation in the Shedhi River basin.

Flooding of rivers in India is linked with the peak monsoons. Investigating the linkage between monsoonal patterns and flood history of various rivers is therefore of fundamental importance in the Indian context. In the present study, the slackwater deposits in the alluvial reaches of the Mahi river basin, western India have been documented. These occur in the ravines incised during the early Holocene on an alluvial surface comprising sediments of Late Pleistocene age. The slackwater deposits occur at elevations up to 20 m from the present river level and extend to about 500 m inland. The carbonate rich sediments forming the ravine cliffs have provided bank stability and the dissections in the ravines have helped in the accumulation of slackwater deposits due to backflooding of the floodwater from the main channel. Recent gullies have incised the sediments and exposed deposits related to major flood events. The best exposures of slackwater deposits have been observed at Dodka. The sediment succession of the slackwater deposits is dominated by bedsets and laminasets of silt and sand separated by colluvial sediments. Four events of flood deposition occurred during the mid to late Holocene. Two units of slackwater deposits, SWD 2 and 4 have been dated by IRSL at 4.6 ± 1 ka and 1.7 ± 0.5 ka. The stratigraphy of these deposits indicates that the first two slackwater units (SWD1 and SWD2) have resulted due to flooding in a regime of intense monsoon. The other two units, however, represent extreme high magnitude floods in a period of low average precipitation.

Resource potential in space and time is dependent upon the hydro-geomorphic dynamics that include topography, precipitation and lithology. Regional geo-climatic conditions control the distribution and availability of water resources and their development requires a scientific evaluation of potential and terrain appropriate structures. In this context, the northwestern region of the Indian subcontinent has diverse geomorphologic characteristics ensuring a wide disparity in the distribution of surface water resource. The rivers are seasonal and the flow is dependent on the rainfall which varies from less than 100 mm in the arid land to more than 1000 mm in the eastern hilly areas. Based on the variations in these parameters, the area is divided into five hydro-geomorphic units 1) Dunal Plains of Thar, 2) Semi-arid to Arid Alluvial Plains, 3) The Eastern Hill Ranges, 4) The Plateau and Pediments (buried/exposed) and 5) Coastal Plains. The major issues in harnessing the surface water include seepage/evaporation losses in the plains and excessive runoff due to steep slopes and hard rock lithology in the hilly areas. Unavailability of water in the downstream due to damming of rivers, changing land use and obliteration of drains in the catchment of ponds are some human induced major issues in this region. Ample groundwater resource and advent of tube wells led to neglect of the existing water harvesting structures as well as surface water bodies, but now, the ground water is fast depleting. There is good surface water potential at least in parts of the region, but its rejuvenation needs impetus. The water availability and security can be improved adopting a basin perspective provided the resource is managed in a holistic and integrated manner at this level.