Satellite-derived bathymetry: a case study of Mombasa Port Channel and its approaches, Kenya

Bathymetry refers to the depth of the water column in relation to sea level. It is fundamental in marine spatial plan- ning, resource exploration and sustainable management of marine resources. It is also vital for safety of navigation, and planning of coast-based infrastructural developments. However, acquisition of bathymetry data is very expen- sive due to the cost of equipment, expertise and technology needed to collect data and produce maps. Satellite-de- rived bathymetry (SDB) therefore offers an opportunity to generate shallow water bathymetry at extremely reduced costs, mainly due to freely-available multispectral satellite imagery and open-source processing software. This paper presents the application of an already developed and published shallow-water bathymetry derivation model and protocols. The results indicate that the technique could be effective for mapping shallow water bathymetry, with higher accuracy in low to non-turbid waters. The SDB of Mombasa Port was identical to the official charted depths upon comparison, with a R2 value of ~90% and a RMSE of 1.61 m. SDB maps can be categorized as medium resolu- tion due to their relatively low spatial resolution. SDB cannot be used as a stand-alone hydrographic tool but it rather offers a viable reconnaissance solution for mapping shallow coastal waters where hydrographic data gaps exist.