Within the Marine division sector to the north of Seoul lay the junction of two major rivers, the Imjin and the Han, and a portion of the broad fertile valley fed by the latter. Flowing into the division area from the east, the Imjin River snaked its way southwestward to the rear of JAMESTOWN. At the northeastern tip of the Kimpo Peninsula, the Imjin joined the Han. The latter there changed its course from south to west, flowed past Kimpo and neighboring Kanghwa-do Island, and emptied eventually into the Yellow Sea. At the far western end of the division sector the Yom River formed a natural boundary, separating Kanghwa and Kimpo, as it ran into the Han River and south to the Yellow Sea. To the east, the Sachon River streamed into the Imjin, while the Kongnung emptied into the Han where the MLR crossed from the mainland to Kimpo. In addition, two north-south oriented rivers flanked enemy positions opposite the Marines and emptied into major rivers in the Marine sector. Northwest of Kimpo, the Yesong River ran south to the Han; far to the northeast, just beyond the March 1952 division right boundary, the Samichon River flowed into the Imjin. Although the rivers in the Marine division were navigable, they were little used for supply or transportation. The railroads, too, were considered secondary ways, for there was but one line, which ran north out of Seoul to Munsan-ni and then continued towards Kaesong. Below the division railhead, located at Munsan-ni, a spur cut off to Ascom City. Roads, the chief means of surface transport, were numerous but lacked sufficient width and durability for supporting heavy military traffic. Within the sector occupied by the Marines, the main route generally paralleled the railroad. Most of the existing roads south of JAMESTOWN eventually found their way to the logistic center at Munsan-ni. Immediately across the Imjin, the road net was more dense but not of any better construction. From the logistical point of view, the Imjin River was a critical factor. Spanning it and connecting the division forward and rear support areas in March 1952 were only three bridges, which were vulnerable to river flooding conditions and possible enemy attack. Besides intersecting the Marine sector, the Imjin formed a barrier to the rear of much of the division MLR, thereby increasing the difficulty of normal defense and resupply operations.