creating inputs to part i hec-hms in geohms

Tutorial I: Applied hydrology

Part I

Creating inputs to HEC-HMS in GeoHMS

Kick off and introduction

• Download HEC-HMS and HEC-GeoHMS from: https://www.hec.usace.army.mil/software/

• HEC – HMS is a hydrological-hydraulic software to simulate complete hydrological process

• Software provides a complete set of tools to built a hydrological model

• HEC – GeoHMS is an extension to be used in ArcGIS to develop a number of hydrologic modeling inputs for HEC – HMS

• To work on the inputs a given Digital Terrain Model (DTM) will be used in ArcGIS to discretize the watershed, the river reaches and all the basin characteristics needed to build up a hydrological model

• Follow the tutorial carefully and step by step to understand and carry on with the objective of building a hydrological model

• The second part of the tutorial will be to use the information of the hydrological model to build a 2D hydraulic model in Iber. The model is provided in the website: http://iberaula.es/

https://www.hec.usace.army.mil/software/

http://iberaula.es/

Part I: Creating inputs to HEC-HMS in GeoHMS

• Install the HEC – GeoHMS and follow the step:

HEC-GeoHMS tool


• Add the raster provided into the table of contents:

• Use for loading the raster of the area of study

• The study area is a campsite in the pyrenes

• The name of the campsite is La Mola

• A hydrological model will be built to evaluate a hydrograph in the zone of the campsite


• Add the raster provided into the table of contents:

• Use for loading the shapefile indicating the campsite “La Mola”


• Start with the basin Processing

• Select Fill Sinks to correct cells in the raster with inconsistencies in the elevation data



• Select Flow Direction. It will create a file with information of the drainage direction in the basin



• Select Flow Accumulation. It will create a file with information of zone for water accumulation in the basin



• Select Stream Definition. It will create a file that will define a number of reaches that will be associated to a catchment. As long as less river reaches are defined, less catchments will be created

• In number of cells to define stream use the number 325000



• Select Stream Segmentation. It will create a file with information of the main river reaches



• Select Catchment Grid Delineation. It will create a file with information of the catchment associated to the main river reaches



• Select Catchment Polygon Processing. It will create a shape file with information of the catchment associated to the main river reaches



• Select Drainage Line Processing. It will create a shape file with information of the main river reaches



• Select Adjoint Catchment Processing. It will create a file with the whole domain of the catchment


• Continue with the Project Setup

• Select Start New Project. It will create the new project with the outlet proposed for the catchment studied (Campsite La Mola)



• Select a Project Name and Description and the press OK

• A new windows will pop up asking to select the outlet of the catchment

• As defined before, it will analyze the state of the campsite La Mola. This means that the catchment has to drain directly to the campsite which is in the path of the main river (“Escrita”)

• Next step will be to add the shape file indicating the campsite



• The outlet of the basin is located next to the campsite “La Mola”

• The shape file you need to add is called “LaMola_Campsite.shp”



La Mola



• Disconnect most of the layer except StrLnk and the original DTM and ZOOM IN



• With this tool the outlet can be draw over the StrLnk. It will indicate the outlet of the catchment. From this point upstream the catchment will be discretized


• Continue with the Project Setup • Click OK and the Project Point will be created. Place the outlet over the grid line as shown in the figure. Always try to use long grid lines to place it

• Click on Generate Project



• A new layer is created with new information of the basin


• Continue with the Basin Processing

• Load the shape file Raingage

• The original basin discretized by the tool is divided in 7 subbasins

• The final goal is to create a model with 4 subbasin due to (in part) there are just 4 raingages



• Click the tool Select Futures to select the basins to merge

• Then in Basin Processing press Basin Merge



• The new 4 subbasins will be created that include the direct effect of each raingage

• Short question: is it needed to increase the subdivision of basins?



• The final goal is to have four subbasin that covers the effect of the 4 raingages proposed for the exercise


• Continue in Basin Characteristics

- River length- River slope (in input Shape Grid use RawDEM)- Basin slope (in input Shape Grid use RawDEM)- Longest Flowpath (in input Shape Grid use RawDEM)- Basin Centroid- Centroid Elevation (in input Shape Grid use RawDEM)- Centroid Longest Flowpath- Centroid Elevation (in input Shape Grid use RawDEM)- Centroidal Longest Flowpath

Take into consideration that the RawDEM must be projected. In case is not, go to:

Search folder by folder once clicking on Coordinate System:Projected Coordinate System/UTM/WGS 1984/Northern Hemisphere/WGS_1984_UTM_Zone_31N


• For the Loss Method the Curve Number (SCS) routine will be selected

• In Transform Method the SCS Unit Hydrograph must be selected

• Not Base Flow needed• The Route Method will be

represented by the Muskingum routine

• Later on click on River and Basin Auto name. No other utility will be selected in this tab

• Continue in basin Parameters: here some parameters that are used in HEC-HMS will be added

• Select HMS process:The following methods will be selected:


If you have problems when checking, do not panic, they can be fixed in HEC-HMS

• Click on the tab HMS. Each option (except Grid Cell File and Import) has to be selected to complete the process



• Create a meteorological model selecting Specified Hyetograph



• Select a location for the HMS Project



- You can call whatever name you want to HMS Run Name

- The Simulation Start/End Date Time will be properly setup later on in HEC-HMS, same as the Time Interval

Tutorial I: Applied hydrology

Part II

Importing and setting up the model in HEC-HMS

Part II: Importing and setting up model in HEC-HMS

• Open HEC – HMS and open the project created in ArcGIS (HEC – GeoHMS)

- The project previously created has the extension *.hms. Load it in HEC-HMS


• Open HEC – HMS and open the project created in ArcGIS (HEC – GeoHMS)

- The model loaded consists of a set of elements that represents the processes and parts of a basin

- Wxx represents the subbasins, Jxx the junctions, Rxx the river reaches and the outlet

- Junctions works as nodes that link river reaches and subbasins


• Load the shape files to visualize the subbasins and the river reaches

Right click over the domain

- Load the shape files for river and basin previously created



To fix the view of the model in the viewer go to Maximum Extents



- Set Union Of All Maps and Elements at 25% to obtain the view of the figure


• Checking each element that defines the hydrological model in HEC – HMS

- Subbasin

- Reaches

- Junctions

Information to complete the model (loss, transform and routing) will be calculated with a excel file called “model_data.xls”

Rename the subbasins with W1, W2, W3 and W4, from upstream to downstream. Do the same with junctions and reaches



The basin will later be filled up with information for the Loss and Transform method. Both methods selected are resolved by the SCS formulation (Curve Number and Unit Hydrograph)


• Checking each element that defines the hydrological model in HEC-HMS

The reach element will later be filled up with information for the Routing method. In this case the methodology selected to simulate routing (flow along river reaches) is the Muskingum formula

- The Muskingum parameters are K and X, and must be filled up in the figure of the right side

- For references of the methodology visit HEC-HMS help file. Later on, the K will be calculated in the excel sheet (model_dat.xlsx) and X will be proposed according the river topology



Now the Meteorological Model element has to be checked. Here all the information of the main input (rain) must be set up

- First, in Meteorological Basin, in the tab Basin put YES as an option for Include Subbasins

- In Specified Hyetograph each subbasin will be connected with a raingage that has to be created as time series. The time series is created as it show in the next slide



Creating a Time Series for the rain

- Create 4 Precipitation Gages that may be named same as the subbasins (W1, W2, W3 y W4)

- Each rain gage contains information of the duration and time interval o the rainfall event. Duration and time interval may (must!) be adjusted by the user. Later on it will be explained which rain event to use for each subbasin

- This information has to be completed with the data provided by the excel file “model_data.xlsx”



Creating the Control Specification Model

- The Control Specification Manager creates the simulation time. Here the date and duration of the simulation is set up. The duration has to be always larger than the rain duration. In this case 12 h has to be used

- Due to the rain time interval is 10 min a time interval for the simulation time may be also 10 min. This means that the results will be written each 10 min. The time interval for the simulation is normally selected by the user, most of the time take into consideration the time interval of the rain event



Creating the Simulation Run

- The Simulation Run creates the tool that actually runs the model once all the parameters have been properly set up

- HEC – HMS is able to create several simulation runs that may be very useful when different simulations with different set of data need to be run

- Each Simulation Run will be connected with the Meteorological Model and the Control Specifications created previously. This implies that if you want to create more than one Simulation Run, additional Meteorological Model and Control Specifications must to be created too



Creating the Simulation Run

- The symbol shows that the model is ready to runs


• Preparing the inputs to set up the model in HEC – HMS

- All the information needed is in the excel file named model_data.xlsx. Some previous calculations must be carried out to create enough data to feed the model up

- The case of a campsite in the Pyrenees that suffers flood during rain event will be analyzed. The name of the campsite is La Mola and it is located at the outlet of the catchment

- The river that flows along the campsite is named Escrita and the closest town is Espot

- The basin and subbasins defined with HEC – GeoHMS in the previous slides and later loaded in HEC-HMS will be the hydrological model of study

- For analyzing the flood, a rain event of a return period of 10 years (T10) will be used as an input in the hydrological model (HEC - HMS) to generate the correspondent hydrograph at the outlet

- The official information says that a rainfall event of T10 yield a peak discharge of 114 m3/s in the zone of the campsite. The task will be to obtain that peak discharge with the built and set up of the hydrological model and the data provided in the excel file (model_data.xlsx). It is also know that the peak discharge for T10 generate floods in the campsite area. The flood analysis will be assessed with the 2D model Iber that will be explained as a second exercise of river hydraulics. This assessment will be carried out with the hydrograph obtained for T10 at the outlet of the basin

- See the following scheme to understand the process


• Scheme of the case of study

- The hyetograph for T10 used as inputs in the hydrological model yield a hydrograph at the outlet (Campsite La Mola)

- Rain events for T10 in alternated block is used in each subbasin

- Each rain event for each subbasin (W1, W2, W3 and W4) has a duration associated to the Concentration Time (Tc) of the subbasin

W1

W2

W3

W4


• Model data in excel

- Read carefully the instructions in the excel file (model_data.xlsx)

- Complete the missing calculations in the excel sheet

- Use the information calculated in the excel sheet to feed up the hydrological model


• Finishing the set up of the hydrological model. Adding the hyetograph in HEC - HMS

- Use the rainfall event for each subbasin of the excel sheet

- In Time Window use the duration time of the hyetograph. Use 10 minutes interval

- Set up the date as shown in the figures. Control Specifications has to be during the same period of the rainfall event (larger)


• Linking rainfall to each subbasin

- In the Meteorological Model, each raingage has to be linked to a subbasin

- This implies that you will have one hyetograph per subbasin with its own duration according to the Tc of that individual subbasin


• Setting up Loss and Transform method

- Remember that the information is in the excel file

- This has to be done for each subbasin

- Use initially the CN presented in the table


• Setting up the Routing method

- Complete the parameter of K with the values calculated in the excel sheet

- Each reach (R1, R2 and R3) must be feed up with the information from the excel sheet

- In the subreaches, complete the following criteria:

R1 = 7 subreachesR2 = 3 subreachesR3 = 1 subreach


• Confirming the Control Specifications

- Set up the Control Specification as showed in the red rectangle

- Things to remember!!!

Include subbasins = YES

Replace missing = set to default


• Run the model

- Run the model following the instructions in slide 50

- Check the hydrograph at the outlet (right click)

creating inputs to part i hec-hms in geohms

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