Town officials are hoping for a big turnout at this Tuesday’s meeting in Hingham Town Hall to discuss the ongoing appeal of federal flood maps. “Most folks won’t be impacted, but those that are will see some pretty significant reductions if [the Federal Emergency Management Agency] ends up approving’’ the appeal, said Abby Y. Piersall of the Conservation Commission. As part of the appeal, GZA GeoEnvironmental Inc. looked at new FEMA flood maps and attempted to rebut some of the predicted flood levels. The new maps have extended the flood plain significantly, and greatly increased the predicted water table during storms for coastal homeowners. The engineers “basically looked at FEMA’s entire study and got more specific with the topography, so what we believe as a town is better information about the elevation extent and coastal flood plains,” Piersall said. Piersall also urged homeowners with specific property questions to call the commission directly.