Inner Terai Valleys of Nepal

The Inner Terai valleys lie between the Sivalik Hills and Mahabharat Range. They hold flat plains with winding rivers that shift their courses from time to time, running northwest or southeast along the axis of the Sivalik Hills. ==Climate==

The Terai has a humid, subtropical climate. The mean annual rainfall at the Rampur weatherstation in Chitwan was between 1995 and 2006. More than 80% of the total annual rainfall occurs during the monsoon season from June to September. Average temperatures ranged from in January to in June. In the past, the inner and outer Terai were a formidable barrier between Nepal and potential invaders from India because marshes and forests were infested by anopheline mosquitos that transmitted virulent strains of malaria, especially during the hot spring and rainy summer monsoon. == History ==

Until the mid 18th century, the Terai was divided into several smaller kingdoms, and the forests were little disturbed. After the unification of Nepal in the late 1760s, the rulers granted large areas of fertiIe land and forest resources to members of the royal family, officials, priests and selected groups of the society. The beneficiaries of these grants had the right to collect revenues from cultivated land and forest products. They appointed tax collectors who were also responsible for reclamation of land and establishment of settlements. In the late 1920s, the Rana rulers ordered the clearing of forests and extraction of timber for export to India in order to collect revenues. Cleared areas were subsequently used for agriculture. After malaria was eradicated using DDT in the mid-1950s, people from the hills migrated to the Terai. Timber export continued to 1969. In 1970, the king granted land to loyal ex-army personnel in the districts of Jhapa, Sunsari, Rupandehi and Banke, where seven colonies were developed for resettling about 7,000 people. They acquired property rights over uncultivated forest and waste land, thus accelerating the deforestation process in the Terai. ==Environmental issues==

The well-meaning malaria eradication campaign has had unexpected consequences by opening up the Terai region to human settlement. The Inner Terai valleys are home to a rich and diverse ecosystem. Since the early 1990s, however, the forests have been increasingly destroyed because of growing demands for timber and agricultural land. This has led to concerns about the risk of losing many rare plants. The valleys also mitigate the severity of floods on the Gangetic plains. During heavy rainfall forests absorb water. During floods, rivers overflow their banks and flood adjacent forests. Later the forests gradually release water back into the rivers. Deforestation reduces this buffering effect. It also accelerates soil erosion, causing downstream rivers to silt up and overflow their banks. The frequency and severity of flooding in the Gangetic plain and Bangladesh has steadily increased in recent years. Deforestation of the Terai appears to be one of the major causes. The Indian and Nepalese governments are cooperating in measures including construction of barrages and dams in the Terai, such as the Koshi Barrage. However, these efforts may have mixed results. They contain floodwater in the short term, but may increase the problem in the longer term by reducing water velocity in the rivers downstream, and thus accelerating silting and reducing the drainage capacity of the rivers. ==Valleys==

The major Inner Terai Valleys are listed from west to east. Click on the terrain and satellite imagery links to see vegetation, rivers, topography, roads and towns. Western Terai Markers at valleys Jogbudha (J), Surkhet (S), Dang (A) and Deukhuri (E) terrain satellite