Observing spatial heterogeneity in the first national-scale connectivity map of India

Sediment connectivity is a critical concept in understanding sediment transfer dynamics and geomorphological evolution. It refers to the degree of linkages between sediment sources and deposition areas, influenced by hydrological processes, topography and climate. This is particularly relevant in India's complex geological setting. This study presents the first national-scale sediment connectivity map of India, derived from SRTM DEM data (~1km resolution), to observe spatial heterogeneity in sediment transfer. 
The connectivity map revealed a wide range of connectivity values (approximately +5 to -14.5), indicating 19 distinct connectivity levels and Getis-Ord (Gi*) revealed 14 major hotspots clusters with 99% statistical accuracy reflecting significant spatial heterogeneity. Key findings include a.) dichotomy in connectivity in The Western and Eastern Ghats b.) the significant contribution of highland connectivity vectors from the Kumaon Himalayas and badlands from the Chambal River Basin to the Ganga River Basin's sediment load. The map was divided into three key zones:
1. High Connectivity Zones:
•    Himalayan States: Regions like Jammu & Kashmir, Himachal Pradesh, Uttarakhand, Sikkim, and Arunachal Pradesh exhibit high connectivity due to ongoing Himalayan orogeny, erosion, glacial melt, and heavy rainfall. Major rivers (Indus, Ganges, Brahmaputra) transport substantial sediment, contributing to the Indo-Gangetic Plain.
•    Northeastern States: Assam, Meghalaya, Nagaland, and other northeastern states also show high connectivity due to high rainfall and steep slopes, leading to rapid soil erosion and high river sediment loads. 
2. Moderate Connectivity Zones:
•    Himalayan Bordering States: Uttar Pradesh, Bihar and West Bengal, at the Himalayan foothills, act as transition zones. They receive Himalayan sediment but have lower slopes and broader floodplains, slowing water flow and promoting deposition, thus reducing downstream connectivity as part of a "source-to-sink" system.
•    Central India: Madhya Pradesh and Chhattisgarh, on the central plateau, display moderate connectivity. Less steep topography results in lower erosion rates, but functional connectivity might increase significantly during the monsoon due to higher runoff.
3. Low Connectivity Zones:
•    Peninsular India: The Deccan Plateau (Maharashtra, Karnataka, Andhra Pradesh, Telangana, and Tamil Nadu) typically shows low connectivity due to stable geology (crystalline rocks), moderate slopes, and lower rainfall, resulting in reduced erosion and sediment yields.
•    Thar Desert: The arid Thar Desert exhibits low connectivity. 
                                      Understanding these patterns, the interplay between structural and functional connectivity, and the influence of human activities and climate change is crucial for sustainable land and water management. Further research at finer scales and assessment of human and climate change impacts are needed. Future studies should consider multi-temporal DEMs to observe spatiotemporal changes for a more comprehensive understanding.