We calculated parameters for the landslide volume estimation equation and for the relationship between landslide area and landslide depth on slopes underlain by four types of geology where many landslides were occurred by heavy rains on August 2022 in Kaetsu Region, Niigata Prefecture. We discussed the appropriate regression method and the relationship between each parameter and geology. The results showed that a method that performs linearization transformation followed by regression has the potential to appropriately evaluate each parameter. The granite slopes in this disaster and the heavy rain disaster in Hiroshima on August 2014 had constant landslide depth regardless of the landslide area. The rhyolite slopes in Niigata and Hiroshima had different changes in the landslide depth relative to the landslide area, so it is necessary to investigate the lithology and weathering characteristics.