HEC-HMS is a hydrological model that can be used to check the result of a storm based event on a watershed or a continuing simulation. HEC-HMS is allocated model but it deals with a watershed as a conceptual model which contain sub-basin and reach. HEC-HMS is very powerful as they have many options for hydrological calculations and a user-defined is one of your options. One of the uses of the HEC-HMS is to forecast the future urbanization that can occur in a watershed and the matching flood that can happen. HEC-HMS together cannot obtain the places of the flooded area however the hydrograph extracted from the HEC-HMS can be used in HEC-RAS and RAS-mapper to get the inundated map of metropolis scheduled to a certain surprise event. Within this lab, a straightforward simulation will be used to simulate the hydrograph of Tifton watershed.
In order to create a HEC-HMS task, there are components should be added first. The main components that the HEC-HMS require is the basin element which contains the basin properties such as sub-basins, reaches and junctions, the metrological element which contains the rain gages that will be used for precipitation, the control aspect which provides the simulation time frame and the time series component which contains any moment series data such as the hyetograph or hydrograph.
HEC-HMS has four main house windows which will be the component screen, view window, editor home window and message log windowpane. The component windowpane has all the created components so that we can toggle between them. In order to edit the components chosen from the component windows, the editor window can be used and it contains tab but also for global data entry or edit the component menu can be used. The view windowpane shows the determined basin, effect or table. The log meaning shows when there is error or the model has found no problem for example as shown in Figure 1 the log meaning says, "Note 10008: Finish beginning task. " Meaning the task was opened effectively with no problems found.
Figure 1 Log communication of HEC-HMS
As mention before that the HEC-HMS is conceptualizing the watershed, so we will import the watershed image as a history as shown in Figure 2 and draw on it the corresponding aspect. This is a straightforward watershed which has only 1 sub-basin and one shop. the sub-basin is named 74006 and the store is junction in HEC-HMS and there is absolutely no reach used for movement channel routing.
Figure 2 HEC-HMS desktop view
The sub-basin properties should be moved into for HEC-HMS to use in calculations. The main property is the catchment area as the HEC-HMS is using all the catchment symbolled in a single point (sub-basin 74006). The other properties that needs to be entered will be the hydrological computations that the HEC-HMS will use to analyze the hydrograph at the shop of the sub-basin as shown in Figure 3.
Figure 3 Sub-Basin hydrological calculation methods
Canopy is the method used to calculate the water intercepted on the tree that steer clear of the water to attain the ground. The percentage of vegetation extracted from remote sensing is utilized to determine the canopy. With this laboratory, simple canopy method is utilized which need only the original water storage in the tree and the utmost storage that the vegetable can take.
In order to point the surface safe-keeping that can happen in the watershed there will vary methods, in this lab a simple surface is used. The easy surface method is mainly saying how much is the initial storage and the utmost storage. The utmost storage space provide in this laboratory is zero which is inadequate as the surface method can be decided on as nothing instead. To get the parameters of the initial safe-keeping and maximum safe-keeping a site investigation can be done or throughout satellite maps and DEM the top depletions and storage space can be calculated roughly.
Infiltration losses is suggested here as the loss method. Losing method that is widely used is the Horton formula but in this laboratory the soil moisture loss can be used. The soil moisture content reduction method mainly works as the ground dampness content and the maximum infiltration rate of the vadous zone of the earth as well as the groundwater beneath the vadous area depth and the percolation rate from vadous zone to the groundwater and when the groundwater is into two different earth type provide the data to each earth type. In order to get the info because of this method a ground surveying is necessary or from a earlier defined data as the FAO maps or Canada CIRUS maps.
The unit hydrograph for the basin is as yet not known so a man-made hydrograph will be utilized. There are different synthetic hydrograph methods in HEC-HMS, in this laboratory Clark (1945) Hydrograph is used. The Clark Device Hydrograph is split into translation based on synthetic time area curve and time of amount and a reduction of discharge as extra rainfall is stored in watershed. Clark Device Hydrograph is modeled with linear reservoir for baseflow. The variables for the Clark Product Hydrograph is enough time of awareness and the safe-keeping coefficient. Time of awareness can be computed using watershed properties or from prior observations but the storage coefficient most likely will be calibrated.
The linear reservoir is utilized for baseflow separation. Baseflow is linearly related to average storage space of every time interval similar to the Clark product Hydrograph. The linear tank also is used with the land moisture content content as this will depend of water in the groundwater and exactly how it returns back to be a contributed to the hydrograph as a baseflow. The guidelines of the baseflow is hard to evaluate so that it will be most likely calibrated.
In the time series part, a rainfall hyetograph is moved into in the rain gages using the Tifton DSS document given the project. After getting into the hyetograph, the graph can be shown as shown in Figure 4. The hyetograph will then be allocated to the basin in the metrological compenent.
Figure 4 Tifton Hyetograph
In the time series aspect, also the noticed outflow hydrograph of the catchment is joined using the Tifton DSS data file. After joining the DSS file the hydrograph is shown as in Figure 5. The hydrograph should be utilized for model calibration of the anonymous parameters.
Figure 5 Tifton noticed hydrograph
In the meteorological component, the hyetograph is allocated to the sub-basin if there are several rain gage a weighted average can be allocated to each sub-basin. Also in the meteorological part, the evapotranspiration is joined. In this lab, monthly average is used which gives a frequent value for each and every month and equivalent coefficient.
Finally, the control aspect is utilized to determine the simulation period and time period. In the laboratory, regarding to my group quantity which is 15 the related simulation time is used which is from the to begin January 1970 to the thirties of June 1970.
After concluding all the data admittance, a simulation manager is used to create a simulation which is identified by selecting the basin, meteorological and control data to be computed. After creating the simulation, compute is chosen and a note of successful come in the note log -if there is certainly any mistake or warning can look in the meaning log too-.
From the results tab, a global summary can be viewed as shown in Figure 6. The global summation provides drainage area contributing to each sub-basin and each junction and enough time to top and the related peak release as well as the total volume of unwanted rainfall. On this lab, there is only one sub-basin so the sub-basin and junction will have the same properties. The top discharge is 873 CFS and took place in the thirty-first of March 1970 at 1:00 PM. The total excess level is 16. 36 in.
Figure 6 Global Summary
The graph of the sub-basin 74006 shown in Figure 7 show the hyetograph in the top part which consists of red and blue. The red part shows the infiltrated depth as the blue series shows the surplus rainfall depth. Underneath part of the graph shows the hydrograph which involves the baseflow and the surplus hydrograph. The blue sturdy series shows the hydrograph as the dotted red line shows the baseflow. Even as we can easily see that in January all the rainfall is almost infiltrated and there is no excess and that is reflected in the hydrograph as there is no excess hydrograph only baseflow. The peak rainfall events happened at the end of March and May as we can easily see that there surely is a lag time between the optimum of the hyetograph and the hydrograph which represent enough time of this inflatable water to route although watershed to the outlet of the catchment. Even both event in March and May has the same rainfall but the optimum was higher in March due to the infiltration difference. The infiltiration that took place in-may was larger than March as the dirt water content in March was high due to event happened right before the peak event while before May peak event it was dried out for almost 8 weeks.
Figure 7 Hyetograph/Hydrograph of Sub-basin 74006
The hydrograph of the junction shown in Figure 7 shows the hydrograph via each sub-basin the blue dashed line and the total summation of all the hydrographs at the junction the blue range and the observed data the black dotted series. The dashed blue range and the sturdy blue brand are coinciding because there is only on sub-basin that donate to the junction. As shown in Figure 7, the observation and the hydrograph at the junction as almost the same which means that the variables and methods used in the HEC-HMS are representing the truth quite well.
Figure 8 Hydrograph of Junction
HEC-HMS can simulate storm event to get the circulation hydrograph of the catchment. It is important to make use of the sufficient method based on the data supply. The model should be calibrated using the experienced data. HEC-HMS can gives how each sub-basin can contribute to the basin outflow and what changes may happen if the sub-basin changes.
- Hydrologic Engineering Centre (2010). Hydrologic Modeling System HEC-HMS, Quick Start Guide, US Military Corps of Technical engineers, Davis, USA