subsidence<\/a>\u2014for 40 major river deltas worldwide.<\/p>\nTheir satellite data was gathered using InSAR (Interferometric Synthetic Aperture Radar), a powerful remote sensing technique that uses multiple radar images of Earth\u2019s surface to map tiny elevation changes over time. The map offers a high-resolution view of delta-wide subsidence spanning five continents and 29 countries.<\/p>\n
Deltas experiencing the highest rates of subsidence include the Mekong in southern Vietnam, the Nile in northern Egypt, the Chao Phraya in southern Thailand, the Ganges-Brahmaputra in eastern India, the Yellow River in northern China, and the Mississippi River in the Gulf of Mexico. These deltas are home to some of the most densely populated cities in the world, including Bangkok, Cairo, and Kolkata.<\/p>\n
These deltas are sinking about 4 millimeters per year on average, faster than current estimates of global sea level rise. \u201cThis is a really fast rate,\u201d Shirzaei said. A change of 4 mm per year may not sound like much, but over time, it drastically increases the risk of flooding, erosion, and saltwater intrusion (saline contamination of soils and fresh water), he explained.<\/p>\n
While both land subsidence and sea level rise contribute to flood risk, the fact that these deltas are sinking faster than sea levels are rising means that subsidence is the primary driver of their near-term flood risk, according to Shirzaei.<\/p>\n
\u201cSea level rise exacerbates the effect of land subsidence, not the other way around,\u201d he said. \u201cIf you want to come up with an adaptation strategy or create a resiliency plan, this is the data you should look at, rather than projections of sea level rise to 2100.\u201d<\/p>\n
The causes of land subsidence and solutions <\/p>\n
The good news is that land subsidence is much easier to address in the near term than sea level rise. Whereas sea level rise is driven by global climate change, land subsidence is driven by regional human activities such as excessive groundwater pumping or underground mining.<\/p>\n
If communities mitigate these activities and take steps to reverse the damage, they can halt subsidence and rapidly regain elevation. \u201cWe have very good engineering solutions for that,\u201d Shirzaei said. One of the best is managed aquifer recharge, which involves pumping water back into depleted underground aquifers to lift the land surface and replenish the groundwater supply.<\/p>\n
To help river delta communities address land subsidence, Shirzaei and his colleagues hope to tailor their observations for decision-making. Future studies will need to account for infrastructural differences to fully assess the subsidence-driven flood risk across various river deltas, he explained.<\/p>\n
Shirzaei also hopes researchers will eventually be able to map land subsidence across the entire world\u2014similar to Google Earth, but for land deformation. \u201cThis is possible,\u201d he said. \u201cThe satellite data that we use are publicly available data, we don\u2019t pay for it, and we have the technology to process the data and turn them into such useful measurements at [high] precision and accuracy. The only thing we need is real investment.\u201d<\/p>\n
Access to this data will become increasingly important as climate change continues to compound the effect of land subsidence across the world\u2019s coastlines. \u201cHaving this data processed and made publicly available\u2014I think that\u2019s a right that everybody has,\u201d Shirzaei said.<\/p>\n","protected":false},"excerpt":{"rendered":"People have settled on river deltas for millennia, drawn by fertile soil, fresh water, and abundant food sources.…\n","protected":false},"author":2,"featured_media":369968,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[22],"tags":[556,1397,1048,13698,90,16369,56,54,55],"class_list":{"0":"post-369967","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-environment","8":"tag-climate-change","9":"tag-environment","10":"tag-flooding","11":"tag-satellite-imagery","12":"tag-science","13":"tag-sea-level-rise","14":"tag-uk","15":"tag-united-kingdom","16":"tag-unitedkingdom"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/369967","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/comments?post=369967"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/369967\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media\/369968"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media?parent=369967"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/categories?post=369967"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/tags?post=369967"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}