| Summary: | This paper discusses the use of a Geostationary Ocean Color Imager (GOCI) to monitor the spatial–temporal distribution of suspended sediment (SS) along the coastal waters of northern Taiwan which was affected by Typhoon Soudelor from 8 to 10 August 2015. High temporal resolution satellite images derived from GOCI were processed to generate four-day average images of SS for pre- and post-typhoon periods. By using these four-day average images, characteristics of SS along the north of Taiwan coastal water can be tracked. The results show that SS concentration increased in the four-day average image immediately after the typhoon (11–14 August), and then decreased in the four-day average image 9 to 12 days after the typhoon (19–22 August). The mouths of the Dajia River and Tamsui River were hotspots of SS, ranging from 9 to 15 g/m<sup>3</sup> during the two post-typhoon periods. Moreover, the maximum suspended sediment (<inline-formula><math display="inline"><semantics><mrow><mi>S</mi><msub><mi>S</mi><mrow><mi>m</mi><mi>a</mi><mi>x</mi></mrow></msub></mrow></semantics></math></inline-formula>) and its corresponding time (<inline-formula><math display="inline"><semantics><mrow><msub><mi>t</mi><mrow><mi>m</mi><mi>a</mi><mi>x</mi></mrow></msub></mrow></semantics></math></inline-formula>) can be computed using GOCI hourly images for the post-typhoon period from 08:30 on 11 August to 08:30 on 22 August. The results show that <inline-formula><math display="inline"><semantics><mrow><mi>S</mi><msub><mi>S</mi><mrow><mi>m</mi><mi>a</mi><mi>x</mi></mrow></msub></mrow></semantics></math></inline-formula> occurred in the west coastal water within 4 days post-typhoon, and <inline-formula><math display="inline"><semantics><mrow><mi>S</mi><msub><mi>S</mi><mrow><mi>m</mi><mi>a</mi><mi>x</mi></mrow></msub></mrow></semantics></math></inline-formula> occurred in the east coastal water 9 to 12 days post-typhoon. Furthermore, an exponential decay model was used to compute the time when 90% of typhoon-induced SS was dissipated after Typhoon Soudelor (<inline-formula><math display="inline"><semantics><mrow><msub><mi>t</mi><mrow><mn>90</mn></mrow></msub></mrow></semantics></math></inline-formula>). It was found that <inline-formula><math display="inline"><semantics><mrow><msub><mi>t</mi><mrow><mn>90</mn></mrow></msub></mrow></semantics></math></inline-formula> in the mouths of the Tamsui River and Heping River was the longest among all coastal waters of our study area, with a range of 360–480 h. River discharge and ocean currents with suspended sediment concentration are discussed.
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