全省主要河川流域地質資訊系統建立(I)

Abstract

本計畫主要目的在於建置全省主要河川流域地質資訊系統之相關地質圖層，做為河川流域整體規劃的應用資訊。本案執行之整體構想，在於考量河川管理規劃的相關地質條件，以建立圖層架構，蒐集既有地質資料建置於各河川流域的相關地質圖層內。 針對地質與河川之相互影響，本計畫中探討說明河川系統之平衡狀態、河道變遷之機制、台灣地區常見之水系型態發展特性、河川流域發展產生之地形特色以及環境敏感地質對河川治理之影響，並摘要敘述台灣地區地質之主要分區及包含岩層種類於附錄中。 本計畫完成頭前溪河床河道地質判釋分區及繪圖，判釋之方式包含立體對及正射影像，說明藉此方式研判河道現況確屬可行。 在河床質底床粒徑調查方法探討方面包括：河床質粒徑分佈與地形地質之關係、河床質顆粒型態與河道類型之關係、河床質採樣與分析之不確定性、河床質採樣分析方法之介紹、以及完整的河床質的採樣分析程序。 台灣的的特有地形、地質及氣候條件，造成土壤流失量偏高，崩坍地對土壤流失佔有重大之影響。現有之集水區沖蝕模式，無法完全適用於面積、地形起伏量大之水庫集水區沖蝕量計算。探究現況之下土砂量評估模式應用之困難性在於台灣缺乏推估土砂產生量之相關參數之長時期觀測記錄，衍生之問題便是無法正確的訂定各經驗公式所使用之參數。 本計畫已收集國內各主要資料產製單位之地質相關圖資，並建置成下列六大圖層：1.河川流域數值地形圖層、2.基本地質圖層、3.敏感地質圖層、4.河床質圖層、5.地質探查資料圖層、6.參考資料圖層。建置工具採用ArcView 9.0，包括ArcMap和ArcCatalog兩個主要模組，可以管理和展示向量圖籍、影像與屬性資料，匯集空間資訊和屬性資料，並在系統之中加以連結，以方便人員查詢，並且可隨時更新或擴充資料。建置之成果在頭前溪流域方面共計11大類65圖層，其他九個流域亦都已建置三十餘層以上之圖資。

This project aims to establish the geology data-base and layers in the geographic information system (GIS) of ten major river basins in Taiwan. The major purpose of the project is to provide a platform for common collection and acquisition of geologic information available for the planning and management in each river basin. In this project, a large amount of available geology information collected from various sources was compiled to establish the geology layers in the river-basin GIS. The established GIS layers include: (1) layer for DEM, (2) layer for basic geology information, (3) layer for sensitive geology, (4) layer for river-bed, (5) layer for site-investigation data, and (6) layer for reference data, among other GIS layers. The GIS system in the Tou-Chien River basin contains eleven categories with 65 layers in total. The GIS systems in nine other river basins contain more than 30 layers in total. In addition to the establishment of the geologic GIS system of major river basins, this project also discussed a few river-basin related geologic subjects as follows: (1) The roles of geology of river basin on major river characteristics: The roles of geology of river basin on river morphology, the equilibrium of river system, river evolution, and river type were discussed. These characteristics may largely affect the planning and management works in a river basin. Real examples in Taiwan were used to demonstrate the relevant subjects. (2) Usage of aero-photo for the interpretation of river conditions: Demonstrated by a serial of case studies on Tou-Chien River, it was demonstrated that aero-photo could help to interpret the river conditions. (3) Site-investigation for river-bed materials: Appropriate approaches of site-investigation and interpretation for river-bed materials were reviewed and discussed. (4) Soil loss: The soil loss in a river basin usually depends heavily on climate geomorphologic, and geologic conditions in the river basin. Due to the severe climate and poor geology conditions often encountered in Taiwan, the soil loss in a river basin tends to be much greater than those occurred in other regions in the world. Approaches commonly used in other countries are not necessarily appropriate for directly adoption. Common approaches for the estimation of soil loss in a river basin were reviewed and discussed.