鹽港溪大斷面測量

鹽港溪排水發源於新竹縣寶山鄉和峨眉鄉交界的油車陂，全長約12.0公里，集水區面積約40.5平方公里，為新竹與苗栗交界之重要河川，自民國78年公告為次要河川，82年由前臺灣省水利局完成「鹽港溪治理基本案」並公告其治理計畫線，於94年奉經濟部將鹽港溪排水列為中央管區域排水。 渠道測量為治理與管理必要工作，其中大斷面測量更屬必須定期辦理之項目，為利管理單位了解渠道通洪能力、現有堤防高程及渠道變動情形等，爰辦理「鹽港溪大斷面測量」計畫案，其主要工作項目為：1已知控制點檢測及引測、2斷面樁埋設與測量、3大斷面測量、4防洪及跨渠構造物調查、5彩色航空攝影、6河床質調查與分析、及7計畫渠段土地利用現況圖製作及分析、8相片基本圖收集及計畫渠道範圍數化、9河川型態影像判釋分析、10計畫渠段排水圖籍整理、現有構造物安全分析及檢討、11渠道沖淤變化及水理模式建置、12Photomesh3D模型建及互動式3D GIS成果建置等工作。 本案於計畫執行期間完成工作項目如下： 1.測量作業部分： 於測量作業方面共計1檢測已知平面控制點5點、2檢測已知高程控制點5點、3測設斷面樁284點及航測標15點、4完成142處斷面測量及構造物調查作業（護岸型態、跨渠構造物、防洪構造物及流入工等調查）、5完成彩色航空攝影測量（數值正射影像圖、1/1,000數值地形圖、DEM成果）、6完成鹽港溪排水圖籍整理計38幅、7依內政部最新分類標準完成鹽港溪排水計畫渠段土地利用現況圖製作、8收集農航所92年度拍攝8幅像片基本圖並進行渠道數化、9Photomesh3D模型建置、10互動式3D GIS成果建置等作業。 2.河川型態影像判釋分析： 利用計畫區域之正射影像配合本案產製之數值圖資，依航照判釋技術辦理影像判釋，並分析水岸情況、河床質地、水系型態、水流棲地及跨渠構造物等，期能明瞭生態系之環境限制因子，作為未來營造多樣化棲地之參考。 3.河床質採樣分析： 鹽港溪排水河床質調查計10處，依採樣分析結果推估曼寧糙度係數n值範圍為0.013~0.018間。 4.水理分析： 鹽港溪排水為中央管河川，保護標準依照10年重現期之洪峰流量，其通水能力檢討之水理演算模式擬採用美國陸軍工程師團水文工程中心(Hydrologic Engineering Center,U.S. Army Corps of Engineers)所發展計算水面剖線之數值模式HEC-RAS模式，曼寧糙度係數n值依河床質報告分析成果範圍為0.013~0.018間，因未能充分反映水道內植生狀況、渠道阻礙與變化等情形，根據現勘狀況與參考周文德n值之經驗數值及98年規劃報告後，綜合上述分析及治理一致性，水理演算範圍之曼寧糙度係數採0.025~0.035。另鹽港溪排水出口因位於出海口，起算水位依據附近中央氣象局新竹潮位站（位於南寮漁港內）歷年統計資料而得，採7-10月大潮平均高潮位EL.2.3公尺起算。 5.現有構造物安全檢討： (1)堤(岸)頂高及防洪構造物安全檢討： 目前鹽港溪排水現有防洪建造物計有計有左、右護岸各9,385公尺。經水理演算成果可知，以南興橋為界，南興橋往下游處僅有零星之出水高不足，往上游處由斷面32至國1高速公路橋斷面44前，愈往上游愈有出水高及堤高不足之趨勢，其中斷面41至斷面43皆有堤高不足之情形，其餘皆能滿足各自河川保護標準。 (2)跨渠構造物安全檢討： 本案調查之跨渠構造物共計有19座橋，其中中興橋、民德橋、新豐橋跨距不足，南興橋、義豐橋及新豐橋梁底高程不足。 6.渠道沖淤變化變化分析： (1)縱斷面比較： 比對94年及104年斷面測量成果河床沖淤變化，斷面00~斷面02、斷面02-2~斷面06、斷面16-1~斷面16-2以及斷面46-2~斷面46-3呈淤積現象，其餘斷面則大多呈沖刷現象。其中，南興橋上游斷面呈沖刷現象是因工程施作所致，並非自然沖刷。 (2)輸砂變化： 本案輸砂變化採NETSTARS進行分析，NETSTARS為擬似二維水理輸砂模式，以不同重現期距洪峰流量，進行鹽港溪排水之輸砂模擬分析。 (3)橋梁局部沖刷深度： 橋梁局部沖刷深度、束縮沖刷深度及一般沖刷深度三者總和即為各橋梁之沖刷深度總量，成果顯示各橋梁沖刷深度總量介於3.89m(鐵路橋)~5.65m(國1高速公路橋)間，供相關單位檢視橋梁深度是否充足。 (4)渠道變遷分析： 將91年、99年、101年及103年流路予以數化，繪製成鹽港溪排水流路變遷圖，其成果顯示91年流路於多處明顯超出護岸及99年於新城橋上游處些微超出護岸外，其餘年份流路並無明顯太大變化，其中99年之流路變遷主要為辦理工程所致，其變遷之部分於治理計畫完成後已無此情形。

Channel measurement for the governance and management of the

necessary work, including large cross section measurement is necessary to

handle projects on a regular basis, to facilitate the management units

understand channel water capacity, changes in the elevation of existing dikes

and channels, and so on, for " The achievement report of a cross-section

survey for the Yan-Gang-Si Drainage " program, in this case work completed

during the implementation of the scheme are as follows:

1.the measuring section : measurement job aspects amounted to (1)

detection known plane points 5 points, and (2) detection known

elevation points 5 points, and (3) measurement section pile 284 points

and the aerial standard 15 points, and (4) completed 142 at section

measurement and the structure real survey job (revetment type State,

and across Canal structure real, and flood control structure real and the

into workers, survey), and (5) completed color aviation photography

measurement (numerical are shot image figure, and 1/1,000 numerical

topographic maps, and DEM results), and (6) completed drainage map

identificatications finishing meter 38 site, and (7) Complete salt Canal

Creek drainage in Yan-Gang-Si current status land use mapping, and (8)

the collection of 8 photos map and channel number, and (9)Photomesh

3D model construction, and (10) interactive 3D GIS build operations.

2. analysis of river morphology image interpretation : Orthophoto of the

planning region in line with the value of production, and on aerial photo

interpretation techniques to handle image interpretation, and analyze

water, River Plate texture, drainage patterns, stream habitat and cross

drainage structures, clear of ecosystems and environmental factors, as a

future reference to create diverse habitats.

3. analysis of bed material sampling: 10 bed load survey meter, according

IV

經濟部水利署第二河川局

鹽港溪大斷面測量

to the results of sample analysis estimates the manning roughness

coefficient n values in the range of 0.013~0.018.

4. water analysis: Water capacity hydraulic routing mode used HEC-RAS

model for review, manning roughness coefficient n-value mining

0.025~0.035. Other exports because it is in the sea, tide starting water

level recovery in July-October the mean high tide level EL.2.3 meter

run.

5. the existing structure safety review :

(1) Bank top security review and flood control structures: At present Salt

Creek drainage of the existing flood control structures include include

left and right bank 9,385 meters. By water acting calculus results

known, South XING Qiao for territories, South XING Qiao to

downstream at only has sporadic of water high insufficient, to

upstream at by section 32 to country 1 highway bridge section 44

Qian, more to upstream more has water high and the di high

insufficient of trend, which section 41 to section 43 are has di high

insufficient of case, remaining are can meet their river protection

standard.

(2) safety review cross-channel structure: Investigation of the case and

cross-channel structure of a total of 19 bridges, the Insufficient span is

Chung-Hsing bridge, Ming-Der bridges and Hsing-Fung bridge,

Nan-hsing bridges, I- Fung bridges and Hsing-Fung bridge height less

than at the end of it.

6. analysis on channel scouring and silting variation change:

(1) the profile comparison: Than on 94 and 104 section survey results

Riverbed changes, section 00~ section 02, section 02-2~ section 06,

section 16-1~ section 16-2 and section 46-2~ section 46-3 deposition

phenomena, most of the remaining sections are flush. Among them,

Nan-hsing bridges upstream sections were scour phenomenon is

V

經濟部水利署第二河川局

鹽港溪大斷面測量

partly due to engineering applied, not natural erosion.

(2) sand changes : lose sand mining NETSTARS analysis in the present

case, NETSTARS losing sand for quasi two dimensional models with

different return periods from the peak flow, simulation analysis of the

Salt Creek drainage of sand lost in Yan-Gang-Si Drainage.

(3) bridge local scour depth : bridge local scour, contraction scour the

beam depth and general scour the sum total scour depth is the depth

of each of the three bridges, the achievements show the total amount

of each bridge scour depth between 3.89m (railway bridge) ~ 5.65m

(highway bridge) .

(4) Channel Change Analysis : 91 years, 99 years, 101 years and 103

years of the number of flow paths to be drawn into a transition

diagram, the results show significantly exceeded 91 years in many

revetment and 99 years in Shing-Chen bridge upstream revetment

slightly beyond, the rest of the year the flow path.