Delta subsidence

Delta subsidence is the gradual lowering of a river delta as its sediments compact, sediment supply declines, or land is removed by natural or human processes.

Sediment compaction: The reduction in sediment volume as grains rearrange or pore fluids escape under pressure. Burial compresses delta deposits, lowering the surface even when sediment remains in place.
Coastal flooding: The inundation of coastal land by seawater during storms, high tides, or rising sea levels. Lower delta elevations allow floods to reach farther inland and occur more often.
River delta: A landform built where a river deposits sediment as it enters a standing body of water. The delta is the depositional system whose surface elevation declines through subsidence.
Interferometric synthetic-aperture radar: A satellite radar technique that maps surface deformation by comparing the phase of repeated radar observations. It reveals spatial patterns of delta sinking over broad areas.
Delta plain: The low-gradient land surface built by river channels and sediment deposits within a delta. Subsidence varies across the plain as sediment thickness, grain size, and human activity change.
Groundwater extraction: The removal of groundwater from an aquifer by pumping or other means. Pumping can compact water-bearing layers beneath deltas and accelerate land lowering.
Saltwater intrusion: The movement of saline water into freshwater aquifers, soils, or surface-water systems. Subsidence can increase marine reach into delta groundwater and agricultural soils.
Porosity: The fraction of a material's volume occupied by pores or other voids. Pore space in delta sediments can collapse as sediment layers are buried or drained.
Global Navigation Satellite System: A satellite-based positioning system used to determine locations and track their changes over time. Continuous GNSS stations measure vertical movement at specific delta sites.
Sediment yield: The amount of sediment a drainage basin delivers to a river or outlet over a stated period. Changing yields make it uncertain whether future deposition can keep pace with sinking.

Linked from 6 pages