滯洪及沉砂池設計常見問題

Abstract

對於開發所導致過量地表逕流及泥砂的處理，須根據「水土保持技術規範」規定設置適當之滯洪沉砂設施，以降低因開發而增加下游地區洪峰流量及泥砂之衝擊。因此滯洪沉砂設施便成為水土流失控制成敗之關鍵；完善之水土保持相關法規、技術規範及設計和專業技師在水土保持業務上所擔負之責任與角色就益顯重要。 本研究重心為藉彙整水土保持計畫審查意見有關於滯洪沉砂設施的部分，予以分類、統整、整理分析常見審查意見討論並提出建議，提供水保技師與相關人員參考。根據本研究整理結果發現五大常見問題：各部分入流及出流的銜接與高程不當、滯洪量或泥沙生產量估算錯誤、排放口公式使用錯誤、滯洪量體或沉砂量體計算錯誤、攔汙柵型式不當，由此可知設計者在此部份之設計較易發生疏忽，因此，未來從事設計或審查時應加強考量此部份，藉此提高滯洪沉砂設施設計品質、降低犯錯之可能、縮短審查流程，以促進提高整體水土保持工作之品質與效率。

To cope with excess surface runoff and sediments elicited by land development and reduce the consequent increase of peak flows and sediments downstream, proper detention and deposit facilities should be constructed based on Soil and Water Conservation Technical Guide. In other words, detention and deposit ponds are the key preventers of water loss and soil erosion. Besides, applicable laws and regulations of soil and water conservation, proper designs and engineers' professionalism are also crucial in this matter. This research paper is targeted at the collection and analyses of all detention and deposit pond related issues covered in investigators' reviews of soil and water conservation plans. Most frequent problems and reviews would be analyzed, and potential solutions and advice discussed as reference for all soil and water conservation professionals. The research findings reveal the following five most frequently encountered problems—elevation differences between outfalls and infalls, miscalculation of detention volume or sediment yield, misuse of formulas for outfalls, miscalculation of regulated detention volume or regulated sediment yield (safety coefficients included), and inappropriate forms of trash racks. Facility designers and investigators should pay more attention to these most frequently overlooked details so as to increase the quality of detention and deposit facilities, reduce potential mistakes, shorten the time invested in all investigations and promote better quality and efficiency of works in soil and water conservation.