Downstream zone of Mae-On watershed areas always suffer floods every year and more frequency. It covering Sankamphaeng district, Chiang Mai province which is the research area. The objectives of this research were to the study: 1) The main factors and causes which has the effect of the drainage systems of flooding 2) Study the natural occurrence, scope and the effects of floods 3) Designed to improve the drainage system to alleviate the severity of floods.
The research process has studied and review the related research to compile scorecards. In addition of this study has to collect data from the field by survey, interview from the actual situation. After that, take the above information to create and develop scorecards for three groups to analysis the equations form of mathematics and give the weighted average to determine the level of risk area and make scorecards mapping to overlapping with the geographic information system and compared data between assessment with the actual situation in the area of education for accordance with the actual situation.
The result study found:
Upper zone of Mae-On Watershed has the main factor and caused by the heavy rainfall and consecutive period time. The landscape within the image area is mountainous with high slope covered with deciduous forest. Which has the potential for water absorption is low. As a result make Water flows situation occur in immediately, the rate of flows quickly, the current strength. The sediment delivery from high to low. Damage to people who live along the water and water barrier flap damage. Problem solving and alleviate the severity of flood / Flash flood which Watershed Management by creating a fire line including regeneration and repair the forest to absorb water and make the slow runoff topsoil. (2) Improve the rehabilitation of catchment basin pond water and sediment trap to sedimentation, bending and trap sediment, according to the design capacity
Downstream zone of Mae-On Watershed has the main factors and causes from the drainage system network did not have an efficacy because many confluence of several small rivers which shoal and meander and has low levels bank waterfront to support the moderate flood. Result of moderate flood makes the flood overflowing the river bank. The occurrence of water has flow rates are increasing steadily until the overflowing its banks to flood residential areas and agricultural areas. Damage to agricultural production. Problem solving and alleviate the severity of floods overflowed the bank have to creating a barrier for the low river bank area to control the flow of water, flowing only within the drainage channel and create a water diversion channel or Kaem-Ling system to drain water out of the area and can catchment for use in the dry season.
Downstream zone of Mae-On Watershed has the main factors and causes from the drainage system network did not have a efficacy because of another river which is outside Mae-On river basin has converged to lower Mae-On River, which has the restrictive and shoal meander and along with promoting factors in land utilization, which has expanded without direction until the invasion area river. Transport network overlap drainage system. Areas receiving water decreases due to the development of the agricultural area for a residential area, the dam doesn’t have the gate open and close make the flood overflowing the river bank and cannot Drainage from the area make Spoilage Foulest and the spread of germs. The solution and alleviate the severity of floods have to adding a water distribution system to distribute water and improve river conditions to support quantity of water and make it flowing through during the rainy season and management land or land use zones in order to prevent the encroachment river catchment area.