Development of flood maps with remote sensing and GIS terrain applications is just an approximation that cannot be used effectively for regulating construction and development in basins.  There are many features in a basin that constrict or expand flow, such as culverts and bridges, whose dimensions can only be obtained from field surveys. The LIDAR techniques do not have the sensitivity required to properly assess the geometry of these structures. Flood maps also are related to the rugosity of the terrain and channel. This is a varying factor in a basin that only the eye of the experienced hydrologist can estimate in the field with multiple photographs and visual calibration against tables developed in prior times.  I am a fan and user of ARCGIS, and favor using it to develop an initial assessment of the potential extent of a floods in a basin, but not for regulatory or development purposes. Field derived maps are required for those activities.

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Development of flood maps with remote sensing and GIS terrain applications is just an approximation that cannot be used effectively for regulating construction and development in basins.  There are many features in a basin that constrict or expand flow, such as culverts and bridges, whose dimensions can only be obtained from field surveys. The LIDAR techniques do not have the sensitivity required to properly assess the geometry of these structures. Flood maps also are related to the rugosity of the terrain and channel. This is a varying factor in a basin that only the eye of the experienced hydrologist can estimate in the field with multiple photographs and visual calibration against tables developed in prior times.  I am a fan and user of ARCGIS, and favor using it to develop an initial assessment of the potential extent of a floods in a basin, but not for regulatory or development purposes. Field derived maps are required for those activities.

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Hi, Marina.  I think that the GIS approach is a great tool for reconnaissance studies prior to the field work needed to develop relatively accurate flood maps that can be used for planning, regulating and design activities in a basin. Perhaps my perspective is related to living in USA where FEMA (Federal Emergency Management Administration) flood maps are required in essentially all communities for management of flood plains. I can see the tool being applied in countries now developing as a "first cut" to make general decisions on developments. But then this initial interpretations need to be validated with field surveys of historical floods.

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Dear Ferdinand Quinones ,

Thank you for your feedback. I was coming from a perspective that if a lot of precipitation is expected in a certain location, rapid measures, plans and decisions need to be made. Hence, sending experienced hydrologists is not always the best and most viable option.
I, and other members of The Water Network, would appreciate your input and experience. Please feel free to post an Article or a Blog on similar topics so we can all learn something new.

Regards,
Marina

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