曼寧粗糙係數對於河川之通水能力影響極大，但過去曼寧粗糙係數之推估值往往是將河川橫斷面之曼寧粗糙係數視為定值，故過去之推估值並不能隨著水位的高低而變化，亦無法反應出兩岸灘地之變化對曼寧粗糙係數的影響。本研究為了探討河川高灘地之土地利用情形對河川水位所造成之影響，於是利用地理資訊系統（GIS）來對研究區域內高灘地的分佈情況，加以記錄並完成河川之地理資料的數化工作，以便日後研究之過程中能將GIS與模式之運算相互結合，期能藉此推求更精確之結果。

　　　　　The river flow capacity is influenced greatly by the Manning roughness coefficient, but the estimate value of Manning roughness coefficients of the previous studies was considered as a constant value in all river cross-sections. Thus, the previous estimate values could not change with the level of river water surface, and could not reflect the influence of Manning roughness coefficients change with the distribution of berms in the river. In order to evaluate the influenced of water surface level due to the berms development, Geographic Information System (GIS) was used to investigate and record the berms distribution of the research region and to digitize them. It would make the combination of GIS and models, convenient to have the most precise in the forward research process.