Fluvial Geomorphology and Habitat

Transcription

1 Fluvial Geomorphology and Habitat Restoration 河川形貌與棲地復育 Week 7 Part 2: Delineation of Morphological Units 2D Hydraulic MU Delineation 形貌單元劃分 1 Introduction Important task: Mapping and zoning landforms on different spatial scales 2 1

2 Different spatial scales: catchment (watershed) sub catchment river segment ( W) river reach ( W) morphological lunit ( W) hydraulic unit ( W) Microhabitat (< 10 1 W) ( W) ( W) 3 Morphological Units ( W) Hydraulic Units ( W) Microhabitat (< 10 1 W) 4 2

3 Morphological Units ( W) Hydraulic Units ( W) Marginal Deadwater Rapid Boil Pool Fall Riffle Run Glide Chute 桶后溪 Pool Riffle 5 Why delineation of MU so important? MUs Basic units for Understanding physical processes Assessing instream hb habitats Ecohydraulic variables (depth, velocity, shear, substrate ) Controlled by the shape and structure of MUs Instream Habitat Comprised of inter correlated ecohydraulic variables over MUs that attract organisms to reside MUs Revealed by their overlying hydraulics MUs Do not change their spatial pattern with discharge (except for scour and fill under extreme flows) 6 3

4 MU Mapping Flowchart (1) (2) GIS (3) 7 Six Steps to Produce a MU Map 1. Topographic and bathymetric data DEM 2. Determine a relevant low flow regime for MU delineation 3. Run and validate a 2D hydrodynamic model at this relevant low flow 4. Predetermine the number of MU types to be mapped, and estimate the range of each hydraulic variable for each MU type. 5. Usethe model results to createthe the raster maps of the delineation variables (e.g., depth, velocity, Fr, bed shear stress, substrate, cover, ) 6. Apply ArcGIS to delineate MU and produce a MU map. 8 4

5 What is relevant flow for MU delineation? If the flow is too low (almost dry) Only very little of the channel will have identifiable hydraulics If the flow is too high (extreme events) The flow momentum will be too large such that topographic controls on hydraulics are drowned out The resulting hydraulics will have very low spatial variation Channel morphology manifests most clearly at regular low flows. High Flow Low Flow 9 Option 1: Base flow Low Flow Options Base flow: average annual low flow that exists for some measurable extended time period Option 2: Reference flow responsible for channel maintenance such as bankfull discharge. 滿岸流量 A flow of 1/10 to 1/5 bankfull discharge is recommended Option 3: Identify key low flows for ecological lf functions, such as anadromous salmonid migration or spawning Iterative process: Sensitivity analyses may be used to compare and contrast alternatives and quantify uncertainty 10 5

6 How many MUs to be delineated? Most Common Types of MUs MU Pool 深潭 Riffle 淺瀨 Run 順流 Glide 滑流 Pool Riffle Description at low flow Topographic low, exhibiting high depth and low velocity, and low water surface slope. Topographic high, exhibiting shallow depths, high velocity, rough water surface texture, and steep water surface slope. Riffles are generally associated with the crest/backslope of a transverse bar. An area exhibiting moderate to high velocities, high depths, and moderate water surface slope. Runs typically occur in straight sections exhibiting a moderate water surface texture, andare are notlocated over transverse bars. An area exhibiting low to moderate velocities and depths and low water surface slope. Glides commonly occur along the periphery of channels and flanking pools, and can also exist in straight sections of low bed slope. 11 Hydraulic Criteria for MU Classification (Suggested for Hsintien Creek) Pool Depth (m) Glide Run Riffle 0.6 Velocity (m/s) 6

7 More elaborated delineation of MU for lowland gravel cobble rivers 13 Delineation of MU Using ArcGIS 7

8 安裝步驟 所提供 PDF 檔之連結直接按下即可 先建立 Esri 個人帳號 8

9 填入序號碼, 開通啟用 17 下載 10.3 版, 按照 PDF 檔指示步驟安裝 9

10 Data Format 資料格式 File Format CSV: comma separated values 逗點分隔值 (MS Excel) DBF: database file 資料庫檔案 (DB software: MS Access) TXT or DAT:ArcGIS does not read text or data files. Image Format 影像格式 TIN: triangular irregular networks 三角形不規則網角形不規則網絡 RAS:raster 網格圖格圖檔 (pixel 畫素影像 ) SHP: shapefile 向量圖形 ( 幾何圖形位置及相關屬性 ) GDB: geodatabase (ArcGIS 標準 database 數據儲存庫 ) Data Management Suggested Folder Structure Project data (shp, tab, ) workspace shp ras geodatabase tab TIN 10

11 SRH 2D Model Output (for Low Flow) Convert Final SRHN file as Output.csv, save in data folder Create a ModelDomain Shapefile In SMS Map Module, click on ModelDomain File Save As, select tshape Files, save River.shp as a Polygon Shapefile in the project data folder data folder For a check, open the River Polygon Shapefile with SMS. Later, we will use ArcGIS to dissolve the polygons, and get a boundary shapefile. 11

12 Getting Started with ArcGIS Open ArcMap, first make sure the relative pathnames are set as the default to data sources. Menu: File Map Document Properties Check the box after Pathnames field. Also, Menu: Customize ArcMap Options General tab Check to Make Relative Paths the Default for New Map Documents. This ensures that ArcGIS can find necessary files when the Project Folder is copied to and used in other computers. Turn on all necessary features. Menu: Customize Extensions Check all tool boxes. Turn on Windows Catalog and Search, you may dock them to the right, as they are regularly used. Also, Menu: View Data Frame Properties General Tab Units: Set Map and Display units as Meters. 12

13 1. Data Conversion Work Flows Data Table Import Export Events data as data.shp Create TIN Depth or velocity TIN Tin to Raster Depth or velocity raster Clip As clip feature Raster within River Boundary 2. MU Delineation River Boundary Clipped Depth Depth raster Raster Input Add Con Clipped Velocity Velocity raster Raster Raster Calculator MU Masks map of regions with depth and velocity criteria Import Data Import Output.csv by using Add Data or directly drag in, right click on the file, select Display XY Data Click OK. A point file Output.csv Events appears in Table of Contents, and the points are shown in the map window. Right click on Output.csv Events, select Data Export Data. Browse to workspace/shp folder, set the export point shapefile as data.shp Click Save Click OK. Add the exported data as a layer. 13

14 Convert Point Shapefile to TIN Search Window: search create tin Click on Create TIN (3D Analyst) In Output TIN field, browse to workspace/tin folder and set output file as tin_d In Input Feature Class field, select data layer from the dropdown list. Click the Height Field, a dropdown list will show up, select Depth for Height Field Click OK. Convert TIN to Raster Search Window: search tin to raster Click on TIN To Raster (3D Analyst) In Input TIN field, select tin_d from the dropdown list. In Output p Raster field, browse to workspace/ras folder and save the file as ras_d. Output Data Type: FLOAT ; Method: LINEAR ; Sampling Distance: CELLSIZE 1. 14

15 Clip Rater with Polygon Shapefile First, we need to dissolve River.shp asa a single polygon. Drag in River.shp; Menu: Geoprocessing Dissolve Input Features: select River from the dropdown list Output Feature Class: browse to workspace/shp folder and save the output as Boundary.shp Dissolve Feature: select SHAPE_1 Clip Rater with Polygon Shapefile Search Window: search clip click on Clip (Data Management) In Input Raster field, select ras_d layer from the dropdown list In Output Extent field, select Boundary layer from the dropdown list Checkon UseInput Features for Clipping Geometry In Output Raster Dataset field, save the output as ras_d_clip in workspace/ras folder Click OK 15

16 Repeat for velocity: tin_v ras_v ras_v_clip Clipped Depth Raster Clipped Velocity Raster MU Delineation Search Window: search raster calculator Click on Raster Calculator (Spatial Analyst) (1) Riffle (save as Riffle in workspace/ras folder) Con("ras_v_clip" > 0.6,Con("ras_d_clip" > 0,Con("ras_d_clip" <= 0.7,1))) (2) Run (save as Run in workspace/ras folder) Con("ras_v_clip" > 0.6,Con("ras_d_clip" > 0.7,2)) (3) Pool (save as Pool in workspace/ras folder) Con("ras_v_clip" > 0,Con("ras_v_clip" <= 0.6,Con("ras_d_clip" > 1.4,3))) (4) Glide (save as Glide in workspace/ras folder) Con("ras_v_clip" > 0,Con("ras_v_clip" <= 0.6,Con("ras_d_clip" > 0, Con("ras_d_clip" <= 1.4,4)))) (5) Bar (save as Bar in workspace/ras folder) Con("ras_d_clip" <= 0,5) 16

17 MU Raster Map Convert MU Raster to MU Polygon Search Window: search raster to geodatabase Click on Raster to Geodatabase (Conversion) Input Raster: for example, Riffle.ras Output: click on New File Geodatabase icon, name it as MU Geodatabase and add it to Output field click OK. Repeat for other MUs. Search Window: search raster to polygon click on Raster to Polygon (Conversion) Input Raster: for example, Riffle.gdb Output polygon features: for example, save as Riffle.shp in workspace/shp folder Repeat for other Mus. Remember to Uncheck: Simplify polygons 17

18 MU Polygons References Wyrick, J.R., A.E. Senter, and G.B. Pasternack, 2014, Revealing the natural complexity of fluvial morphology through 2D hydrodynamic delineation of river landforms, Geomorphology, 210: EH&G Lab, NTU, 2015, Creating Raster Masks for GCD Analysis, Class Tutorial, prepared for Fluvial Geomorphology and Habitat Restoration