Flooding in Christchurch dyes the ocean pale blue

A massive storm paired with high tides flooded parts of Christchurch, New Zealand, earlier this week. MODIS captured photos of the region on February 22nd, and again on March 6th. The dramatic change in water colour off-shore is the result of loose sediment washing into the city and into the ocean.

Poor Christchurch. The city is built on an alluvial fan. Wet, loose sediments like those found in alluvial fans amplify shaking, so the 2010 and 2011 earthquakes shook the city badly. The shaking damaged flood control equipment, so were unable to sufficiently hold back the inevitable flooding that also goes along with building in a flood plain. During the peak of the flooding, 50 to 100 homes were evacuated and power outages impacted approximately 4,000 people. The hills, already weakened by earlier earthquakes, were prone to landsliding, with at least one cliff-collapse damaging a storage tank.

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Every time disaster strikes, I am amazed and impressed by how much information we can extract from timely satellite imagery. These particular images are not in high enough resolution to pick out patches of standing water or newly-bared slopes, yet the colour of the oceans is a very clear cry that Something Happened Here.

Head over to the Earth Observatory for more. Be sure to click the "View Image Comparison" button for an interactive image where you can use a slider-bar to compare the two photos side-by-side.

Image credit to the MODIS satellite, processed by the Earth Observatory.

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