本研究以構造發展與水系發育之相關性為研究主題，選擇苗栗出磺坑背斜構造地區，探討水系的型式與特徵及相關構造的分布與特性，歸納出出磺坑背斜構造內水系的相關訊息，進而探討地形、構造及岩性對於水系之演育相關性。 水系分析的目的在說明地表水文特性和時間因子之間的關係，本研究使用河谷計測分析和水系空間分析。河谷計測分析以河流等級分析為主；水系空間分析則分為平面空間分析和縱向空間分析，除此之外，本研究亦嘗試進行水系密度分析作為輔證，並於縱向空間分析中佐以SL-index分析，以加強遷急點之判識。 研究結果顯示，出磺坑構造之水系分佈，主要受坡度、構造、岩性、節理及裂隙等因素影響。由水系等級之分佈可知，水系等級與岩性較無相關性，反而受坡度之影響較大。坡度愈陡者，水系等級愈小，坡度愈緩，水系等級愈高。由於本區各支流流域水系等級皆相同，可推論本區各支流其發育所受之時間、空間、氣候等因素影響皆相同。 於河流縱剖面分析中，可歸納出本區遷急點大多為硬岩遷急點，皆與地層交界處有良好的比對關係，並由回春遷急點中可整理出局部的階序，代表本區有多次構造抬升活動。由水系密度分析中發現帶狀之高低值急速變化區域與活動斷層有良好的比對，並可推論出磺坑構造以東一帶可能為活動褶皺。 The main purpose of the study is to confer the relationship between the drainage development and geologic structure in Chuhuangkeng Anticline Area. The conformation of the drainage and geologic structure serves as a basis in discussing the drainage development as affected and related to the local geologic conditions. The purpose of the drainage analysis is to survey the relationship between the characteristics of surface drainage and time factor. Numerical analysis on river valley is used to study the stream orders, while spatial analysis on drainage pattern is to realize both the surficial and longitudinal distributions of the drainage systems in the study area. Drainage density analysis is also done to serve as the assisted data in interpretation. And besides, SL-Index is analyzed in combination with longitudinal spatial analysis to obtain the more accurate knickpoint position. The study results show that the development of drainage pattern is mainly dependent on terrain gradient, geologic structures, rock strata, joint and crack systems. Stream orders are less correlated to rock strata, but they are highly influenced by the terrain gradient. Steep gradients always show lower stream orders, and vice versa. Since most of the different tributary drainage systems in the area bear nearly the same stream order, it is reasonably to infer that they have been developing under the same controlling factors as resulted from the drainage spatial distributions and the climate influence. By judging from the longitudinal stream profiles, most knickpoints in the study area belong to hardrock knickpoints, and are always best fitted to the positions of rock contacts. Knickpoints are distributed in sequential terrace array to reflect frequent crustal uplifts. Drainage density map shows a banded boundary between higher and lower anomaly areas, the belt is right at the place of the active fault line, the east limb of the Chuhuangkeng Anticline may still be in an active folding condition.
