Landsat satellite data revealed a total of 13 small glaciers in the Rambiara basin. These glaciers are characterized by their relatively small size ranging from 3.40 to 27 ha with an average size of 10.75 ha. The glaciers of the basin are further characterized by their high altitudinal snout, situated between 4,000 to 4,320 m a.s.l. The dominant aspect of the glaciers in the basin is N and NE facing slopes, whereas the slope of the glaciers ranges between 17 to 28° with an average slope of 21°. The analysis of satellite data showed that the areal extent of glaciers in the basin has receded significantly from 1992 to 2020. The total area of the glaciers in 1992 was 139.78 ha which shrunk to 125.10 ha by 2020. Therefore, the basin has witnessed deglaciation of about 15 ha or 10.50% during the last 28 years indicating an area loss at a rate of 0.38% a⁻¹. The mean length change of all analyzed glaciers between 1992 and 2020 was 65 m (2.32 m a⁻¹).

The prominent erosional and depositional landforms present in the basin include moraines, trimlines, U-shaped valleys, outwash plains, erratic boulders, cirques, tarns, horsn, aretse, kettle lakes, glacial lakes etc. Such features are the direct piece of evidence of glaciation/deglaciations observed across the basin (Figure 3). There are about 40 cirques present in the basin located near the drainage divide, with the area ranging from 0.05 to 3.60 km² with a total area of 38.40 km². The presence of cirques suggests extensive alpine-style glaciation observed in the Kashmir Himalaya during the Quaternary. The majority of the deglaciated cirques harbor a tarn lake and 4 well-developed horns are also observed in the basin. Glacial lakes are the prominent feature in the basin ranging in size from 0.01 to 0.70 km² with an average area of 0.175 km². These lakes are observed in the cirques and in the valleys carved by glaciers (Figure 4). A few kettle lakes are also present in the glacial outwash with the size ranging from 164 to 2,003.5 m². The glacial troughs down the snout position of the rock glaciers are predominantly U-shaped with varying depth and width. The development of a U-shaped valley is controlled by the weight and velocity of the overlying ice and the bedrock lithology (Fu and Harbor, 2011). The depth of the U-shaped valleys observed in the area suggests that the glaciers in the range have been more than 200 m thick that enabled them to carve deep into the valleys. The mechanism of rock scouring and excavation by glacier action has paved way for the development of overdeepenings, a manifestation of which is observed in the form of a few over-deepened troughs and cirque lakes. A few tributary valleys with their heads marked by the deglaciated cirques, “hang” above the main glacial trough. Trimlines, representing the most recent high-ice stands along the walls of glacial valleys, are observed in the basin. Besides, 40 arêtes associated with present cirque/rock- and paleo- glaciers are observed in the basin, suggesting that after the fragmentation into valley glaciers due to climate change, the glaciers scoured and eroded their respective valleys. Most of the arête ridges are smooth reflecting that glaciers modified these ridges during the LGM.

Lateral moraines of varying size and height are the prominent depositional landforms preserved across the basin. Pertinently moraine ridges formed during the glacier movement, if well preserved, provide vital pieces of evidence of the past extent and the thickness of the glaciers (Huggett, 2007; Mehta et al., 2011; Sheinkman, 2016; Dar et al., 2021; Murtaza et al., 2021). Some of the well-preserved lateral moraines are preserved much downstream from the current snout position of the cirque and rock glaciers. Length of lateral moraines ranges in size between 123 and 1,153 m and the elevation of the lateral moraines measured from the bottom of the U-shaped valleys ranges between 132 and 1,173 m with an average elevation of about 515.6 m. Lots of recent rock glaciers exist in the deglaciated cirques and valleys of the range. The total number of glaciers and rock glaciers present are 13 and 59, respectively, with the average area of glaciers about 0.10 km² and rock glaciers having an average area of about 0.22 km². Besides, a few paleo-rock glaciers are also found. Some well-developed debris cones, alluvial fans, and outwash plains were also mapped in the area. Twenty-six alluvial fans were observed in the upper reaches of the basin. The size of the alluvial fans ranges from 0.2 ha to more than 150 ha. Outwash plains are dotted with kettle holes reflecting continuous deglaciation owing to the current global warming. Loess—a product of glacial environment- intercalated with paleosol profiles are also observed downstream of the basin. Pertinently, loess represents cold and arid glacial climate and the paleosols represent warm humid interglacial climate (Dar and Zeeden, 2020). The effect of glaciotectonics is also visible from vertical incisions and various knickpoints observed in the longitudinal river profile (Figure 5).

The braided index (Bi) measures the degree to which bars and/or islands separate multiple flow paths (Table 1). It is evident from the Bi, that the river is highly braided in downstream reaches, 4, 5, and 6. The Rambiara River has responded to the slight changes in discharge and sediment load, the signatures of which are present in the form of unstable banks (Figure 6), unpaired terraces, river bank shifting, entrenchment, and river sinuosity. The ER values obtained suggest that in reaches 1, 3, 4, and 7 the river has slightly shifted toward the left bank (Table 1). ER values of 2 and 6 reach indicate that there is no bank shifting and the value of reach 7 shows that the river has shifted toward the right bank. The shifting of the river course has resulted in the sinuous nature of the river.

The longitudinal profile of the Rambiara River deviates significantly from a simple concave-up shape. The most remarkable feature of the profile is numerous convexities (knickpoints), especially in the upstream reaches of the river (Figure 5a). While it is obvious that most of these convexities are associated with the braid bars, few are associated with the faults that cut across the river (Figure 2). The stream length gradient index of the river calculated at 15 locations ranges from 36.1 to 2,256.2. The higher SL indicates either hard rock base or relatively higher tectonic activity (Figure 5). The stream length gradient values decrease as we move upstream or downstream from the knickpoints.

The sinuosity index suggests that the river is more sinuous in the lower reaches (6–7 reach). The river flows over the loose unconsolidated fluvio-glacial-lacustrine sediments downstream with the result even subtle modifications in the slope manifest the changes in its morphology. The sinuous behavior and differential entrenchment downstream are attributed to the abundant sediment supply from the erosion of the glacial-borne deposits, moraines, of the range. However, the river is less sinuous in the upstream area (1–4 reach), which was occupied by glaciers during the Pleistocene and the glaciers carved deep valleys presently occupied by the river, hence less sinuosity.

The Cenozoic uplift of the PPR has played an important role in changing the climate of the Kashmir Valley from tropical to temperate type (Dar et al., 2015a). The uplift has probably contributed to cooling and the onset of glaciation in the range (Dar and Zeeden, 2020). Recently, the nature and extent of glaciation of the range have been investigated and few maps have been published on the glacial geomorphology of the area (Paul et al., 2021). However, the relationship between the melting cryosphere, climate change, and the fluvial response has remained unexplored. It is agreed that valley scouring and moraine formation is linked to major glacial phases. For example, during the Early Pleistocene glacial periods, the glaciers advanced much below the mountain ridges, and a large number of moraines (lateral, medial, ground, and terminal) formed in the PPR (Paul et al., 2021) (Figures 3, 4). During the Late Pleistocene glacial phases, for example during LGM, glaciers did not advance much below 10 km from the present-day cirque and rock glaciers (Paul et al., 2021). On the basis of the analysis of the transverse profile of the glacial troughs and the maximum height of the lateral moraines and trimlines, it is evident that the ice was on an average ~200 m thick during the maximum of the glaciation. The presence of numerous recessional (terminal) moraines, small outwash plains, and kettles, advocate continuous deglaciation of the range and the constant decrease in glacial extents (Murtaza and Romshoo, 2021). The presence of the recent rock glaciers and outwash plains up in the glacial troughs indicate the continuity of the deglaciation in the area (Figure 3). During warm interglacial periods, meltwater and sediments from the glaciers and moraines were channeled through numerous small valleys downstream. Since the river discharge has considerably decreased, as observed during the field study, owing to the continuous decrease in the glacial cover (current glacier cover ~1.25 km²) and also due to changes in precipitation pattern (Dar et al., 2013, 2017; Romshoo et al., 2017, 2020), much of the transported sediments have remained preserved especially along the steep valley walls and along the river bed. Terraces preserved along the banks of the Rambiara River contain a thick sedimentary sequence with intervening gravel beds, sand, and, clay lenses (Figure 5b). The coarser sediments/boulder, which makes up the larger proportion of these terraces are composed of the lithologies (basalt, limestone) occurring in the glaciated part of the range. Some of the gravel beds preserved at the top of the river terraces are dated more than 350 kyr old (Bronger et al., 1987). The estimated maximum thickness of these gravel beds is 135 m and is regarded as fluvial-glacial in origin (De Terra, 1939).

Similarly, the occurrence of a large number of alluvial fans at the apron of the confined (hanging) valleys, suggest continuous glacial recession of the PPR. The fan sequence indicates high sediment flux associated with the fluctuating incision and aggradation rates. The distal part of most of these fans is eroded by the streams emanating from the snow-glacier meltwater and precipitation. Morphologically these fans are correlated with the recent deglaciation; however, no chronological data is available. Similar glacio-fluvial fans might have formed in relation to the former-recession episodes. However, owing to the various (four?) glacial periods these fans might have been eroded away during the deglaciation phases.

In glaciated terrains, sediments and surfaces get exposed during the deglacial phases (cold to warm transition) due to receding glaciers and provide a vast source of erodible material that is eroded, transported, and deposited downstream (Cordier et al., 2017). The sediments deposited in the Karewa lake (Hirpur and Nagum Formations) were subsequently exposed due to the desiccation and the draining out of the waters that resulted in base-level change after which the fluvial incision ensued. The alluvial fill incision can be seen from the vertical incision through thick alluvial deposits and river terraces along the course of the Rambiara River. The vertical incision is also influenced by glacio-isostasy; however, this assumption needs further research in the PPR range which is also affected by Himalayan tectonics. Besides, the glacial cycles of the Kashmir Himalaya have been very complex owing to the complex interplay of mountain building, climatic, and hydrographic changes (Brozovic et al., 1997). Therefore, fluvial incision observed in the Rambiara basin is a combination of glacial dynamics, base-level change, glacio-isostasy (typical of glaciated mountain ranges), and the regional tectonic uplift.

The glacial and aeolian system connectivity is important in the production and preservation of windblown dust (loess). Besides, loess deposits are generally closely related to glacial processes and changes in global and regional climate change (Újvári et al., 2016). The downstream area of the basin is characterized by the presence of loess deposits, belonging to the Dilpur Formation of the Karewa Group. At few places, former river terraces are covered with thick loess deposits (Figure 6) and show the presence of interbedded paleosols. Overall, the loess deposits of Kashmir are intercalated with 10–12 paleosol profiles and range in thickness from a few meters to more than 20 m (Dar et al., 2015a,b). The available chronology of these deposits suggests that loess deposition dates back to 350 kyr (Bronger et al., 1987). Since four major glacial periods have been reported from the moraine of the Pir Panjal Range (De Terra, 1939; Holmes, 1989), the rock floor produced during the movement of the glaciers might have provided the basic mineral dust for the deposition of the loess deposits. Pertinently four glacial and interglacial periods have also been recognized in these (loess) deposits (Bronger et al., 1987). A recent study has suggested that the mineral dust for the deposition of the Kashmir Loess was local (Zeeden et al., 2021). Therefore, the loess contains a detailed picture of the changing Quaternary climates and the glacial dynamics of the region.

Rambiara is a braided river having multiple wide and shallow channels, reflecting high sediment load and the non-cohesive nature of bank materials. The melting cryosphere and sediment deposition have profoundly affected the morphology of the Rambiara River as revealed by the thick fluvial-glacial river bank sediments, channel width variations, sinuosity, braided pattern, bank entrenchment, etc. Since the channel morphology is closely related to the volume of sediments deposited, which in turn depends on the water discharge and on the climate change. If owing to climate change, the water discharge increases (due to glacial melting or increase in rainfall), the sediment volume, in the long run, will become exhausted. This will lead to an increase in channel depth, decrease in gradient, and increase in sinuosity. According to Woolderink et al. (2021), a river changes to a sinuous one to maintain a constant channel gradient. Therefore, sinuosity acts as a proxy for the water discharge, sediment flux, and channel migration; the former two factors are determined by the climate (Limaye et al., 2021). The Rambiara River shows sinuous nature and a high braided index in its lower reaches (4–7) where the river gradient is very low (Table 1). Rivers change to the braided patterns as a result of changing gradient, changes in hydrology, sediment load as well as active tectonics. In case of greater in-channel sediment storage, the greater would be the degree of braiding as the sediment inputs modify the channel morphology by altering sediment mobility (Hassan et al., 2007, 2008). In the upper reaches the river is less sinuous and the braided index is also low. In these reaches (1–3) the high gradient and the partly confined settings result in a straight river course and also leads to downstream movement of the sediment load. The sinuosity can also be attributed to the vertical motion, as the range is uplifting at a rate of 10 mm per year (Burbank and Johnson, 1983) owing to the tectonics and glaciotectonics. This is evident from the presence of unpaired terraces and the asymmetry factor of (61.5). Studies carried out on major rivers of the world reflect that these rivers are significantly affected by slight changes in the valley slope even though it seems that the high discharge of these rivers can enable them to maintain a straight course (Schumm, 1979). Therefore, it is believed that the course and pattern of the Rambiara River are affected by the high sedimentation rate brought from the erosion of the unconsolidated glacial deposits, moraines.

Channel widening and braiding can increase if the river course is cut across by geological structures like faults and lineaments (Woolderink et al., 2021). This is observed in the Rambiara River, especially in its reach 4. Here the river is cut across by the Balapur fault (Ahmad et al., 2015) and the river is widest owing to the deformation of the bed and banks associated with the fault activity. This fault is visible on the longitudinal river profile in the form of a knickpoint and also by the abrupt increase in the braided index in this reach (Table 1). The river gradient changes abruptly after crossing this knickzone, with the result deposition of the bed load has resulted in the formation of a large island bar (Figure 5b). The analysis of the terraces reveals that the river might have attained a width of 1,000 m at a few locations during the former glacial periods. The wide nature of the river has resulted in the development of many inland braided bars, especially in the reaches (4–7). The braided index suggested a greater amount of sediment storage within the channel in these reaches. Braiding decreases as the sediment flux decrease or the river are confined in a narrow setting or a fault runs along the river course (Holbrook and Schumm, 1999). The asymmetry factor (AF) indicates that the Rambiara river has shifted downstream to the left of the basin. The basin tilt goes well with the preservation of terraces along the right bank and erosion of left bank terraces (Figure 6b) as well as the entrenchment ratio of 0.9 in the reach 5 of the river.

Glaciers can also influence the fluvial system through glacio-isostasy. However, unlike impacts of glacial activity, the effects of glaciotectonics are difficult to identify especially in the upper reaches of the mountains. Besides, isolating the glaciotectonic signal from the tectonic uplift is challenging especially in the PPR which rapidly rises at an average rate of 10 mm per year (Burbank and Johnson, 1983). Nevertheless, the deglaciation of the range in combination with the tectonic uplift might have led to the vertical exhumation of the range as is evident from the straight mountain fronts and vertical valley walls and few knickpoints which are associated with the faults observed in the Kashmir Valley (Dar et al., 2014). The deglaciation and the consequent isostatic uplift are confirmed from the mountain front sinuosity values obtained across the basin (Table 2). The impacts of glaciation on the fluvial dynamics are superimposed on the long-term tectonic characteristics of the range. The mountain front sinuosity index measured along 42 front segments range from 1.01 to 1.56 indicating active mountain fronts (Table 2). Besides, the presence of numerous triangular facets and a few well-defined lineaments/faults in the basin gives credence to this inference.