By comparing closely some old historical maps with the present topographical ones, the writer tried to investigate the former shorelines of the Fukushima Lagoon, and the expansion of reclamation which followed. The following facts were observed:
In the first place, the shoreline of the lagoon has undergone little change since the Kansei era (1789-1800). A large-scale reclaim work, carried out before the Kansei era, has immediate connection with the cutting of seaside sand dunes in the Matsu-ga-saki region during the Kyoho era (1716-1735). The lowering of the water level made by this cutting was the fundamental condition, of a new reclaim work. After that the water level was kept unchanged, and the mud of the lagoon was dug out with the object of lifting up the boggy ground of paddy-fields near the lagoon, and of manuring. The shore of the lagoon as it stands, as it is comparatively deep, provides only a few good places for new reclamation works. Consequently the deposit action of the rivers flowing into the lagoon year after year had little effect on it and a marked natural change was not noticeable.
Secondly, making paddy-fields by using a small scale “Gabbo, ” was attempted individually by some farm-houses. “Gabbo”, as it is called among the people, means a ‘makomo’-covered, floating island in the lagoon. People make them artificially; at the area chosen a floating island of ‘makomo’ (water oat) is made, on which are accumulated much rubbish and trash after water oat has grown up enough, and reeds are planted on the newly-made ground. When reeds grow thickly there it forms a reeded marsh. Mud brought from the lake is piled up on the reeded marshes, then they are ready to plant paddy. No bank is made around these paddy fields, so they are submerged beneath the water at the time of high water level. However, a farm rent to these fields was by far lower than that to ordinary ones, so reclaiming new farms by this method was eagerely carried on by petty farmers.
Thirdly, though it is a fact that the “Gabbo” was being converted into paddy fields in some parts, it was a technical advancement in rice-culture to give a great change in the Fukushima Lagoon which maintained considerable stability. As power drainage was introduced, draining was stretched from a small area to a larger one. Making use of fertilizer on these paddy fields stopped mud to be dug and brought from the lagoon. A large-scale drainage brought about the lowering of water level, and Gabbo increased to the great degree in some parts of the shallower water in the lagoon. As a result, the lagoon lost its significance to the agriculture in this area and there is given a fair opportunity for the whole surface reclamation work of the Fukushima Lagoon.