They are subject to severe catastrophes, including floods from the landward side and sealevel surges, extreme wave erosion, and storm winds from the seaward side. They are major sedimentary depocenters, the surfaces of which are highly sensitive to changes in climate, marine conditions, fluvial hydrology, foliage development, and tectonism. In modern times, they have taken on new importance. The forms of modern-day deltas vary considerably around the globe and exist in a wide variety of geotectonic, geomorphic, oceanographic, and climatic settings. The possible combinations are infinite, and each delta is a separate case but with analogous components.
Deltas are regions of rapid and significant change in their surface form.
Fundamental scientific problems are encountered in determining which changes are most influential in the steady-state evolution of deltas and what are the process changes resulting from tectonism, important climate shifts, or human activity. Intellectually, these and other questions will remain major challenges to present and future scientists, even though they will be armed with the timely results of superb new technological and conceptual advances. Pragmatically, the continuous demand for hydrocarbon fuels, agricultural land, and renewable resources will drive expanding human activity in deltas throughout the world. Efforts to explore, understand, manage, and exploit these complex coastal sedimentation sites will most certainly be maintained and will likely intensify in the coming years. Imagery from spaceborne sensors is even now being used to monitor, analyze, and understand these important sedimentary deposystems.