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7/27/2019 Training Hand Out

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MIKE 11 HD and RR Practical ExercisesA series of practical exercises, based on exploring and revising the original PUB model covering the

whole Marina Barrage catchment.

Exercise 1: Adding & georeferencing a background image in your Nwk file

a) Add a background image to the network file as a useful referenceb) Georeference the added imagec) Can also add the sub-catchment polygon shapefile

The image (MarinaCatchment.jpg) and a text file containing the georeference coordinates (Image

georeference.txt) are located in: \\PUB_Training_Material\2_ReferenceImage\

Catchment shp (NAM_Catchments.shp): \\PUB_Training_Material\2_RRCalibration\Catchments\

Adding layers: Layers Add/Remove

Editing layers: Layers Properties

Note that the map projection used for the network file in general, and that specified for the

background image(s) used should be the same. Other image files (bmp, gif, png, tif), shapefiles (shp)

and grid files (dfs2, dt2) can also be added as background layers.

The properties (colour, opacity, thickness, etc) of added layers can be edited as necessary.


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Exercise 2: Setting up a Rainfall-Runoff (RR) file using NAM methodology

Since the Marina catchment is a relatively complex system, a simplified NAM calibration (looking at

the Singapore River catchment only) will be performed, as an intro to using NAM for RR modelling.

Suppose you have measured discharge data (m3/s) for a point along Singapore River, and rainfall &

evaporation data over the same period. Based on the known catchment area draining to that

location, (e.g. from a shapefile), set up and calibrate a simple NAM model using the provided data.

a) Open a new Rainfall-Runoff file (.rr11), change to Basin View (View Basin View), andimport the NAM_SingaporeRiverCatchment shapefile, (Basin Work Area Import Basin

Definitions). You can test the integrity of the polygons using the Test Fill Catchments tool

( ), and then convert them to actual catchment extents using the Create Polygon

Catchments tool ( ), remembering to choose NAM catchments. Rename the main gauged

catchment, (in the west), to SR, (the others can be left as they are).

b) Next specify your rain gauges, (Create New Stations tool ), based on the table below.Note that youll first have to extend your working area to fit in all the rain gauges and

catchment polygons, (Basin Work Area Resize Work Area).

Gauge S31 S71 S72 S77 S92 S111 S118 S120

X 27,571 22,345 29,659 25,638 23,002 28,311 29,421 26,293

Y 28,308 30,545 28,503 30,686 29,724 32,527 31,343 32,347

c) Calculate Thiessen polygons based on available rain gauges, (Basin Work Area ThiessenOptions), & check resulting polygons using the Thiessens polygons tool ( ), clicking on

each catchment in turn to see which gauges are contributing rainfall to that catchment (rain

gauge & polygon edges shown in red) and which are not (shown in green).

d) Calculate weighted rainfall for each catchment, (Basin Work Area Calculate MeanPrecipitation), and then to save time for future simulationsuncheck the Weighted

Timeseries column in the RR Timeseries table tab, (only needs redone if inputs change).

e) Specify on Catchments tab that you want a Calibration Plot for catchment SR and thenon NAM Autocalibration tab, check the Include autocalibration. Since were looking at a

small urbanised catchment, we might confidently adjust the lower and upper bounds for

some parameters, (e.g. Umax: 0.1 to 10, Lmax: 0.1 to 100, CQOF: 0.5 to 1, CK12: 1 to 50).

f) Run this .RR11 file and evaluate the RR Calibration results, (comparison of simulated andobserved discharge time-series and also accumulated discharge volumes).

g) Impact of varying autocalibrations objective functions? (e.g. peak/low flow RMSE)h) Impact of varying NAM parameters? (e.g. CQOF similar to runoff coefficient / SCS CN)


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Exercise 3: Run Original (unmodified) model and evaluate results

Starting with original model, run it once, evaluate the results & discuss how it might be improved.

Note: the only change made to the model so far is to reduce the value of delta from 1 to 0.85, (0.85

is the maximum recommended for models with tidal influence see excerpt from MIKE 11 Manual).

\\PUB_Training_Material\0_OriginalModel\

For example, consider the Kallang River longitudinal profile, with both water level and discharge

displayed, (on different y-axes), to evaluate these results.

Explore the results further:

Longitudinal profiles along other river/drain branches Hydrographs at various points in network Water level plots Discharge through structures Compute and display 1D flood results Instabilities (in water level/discharge)?


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Exercise 4: Improve model schematisation

For every cross-section inserted, a h-point is generated, (with an additional Q-point in between that

h-point and the h-points upstream & downstream). Using more cross-sections to describe your

channel geometry will thus result in more computation points & slower run times, and may also

cause instabilities in your model, (especially if there are major changes in invert level or conveyance

between the adjacent cross-sections). When inserting/editing cross-sections, its important to

remember:

Objective is not to represent the physicalstructure of the drain as realistically as possible Objective is to schematise the drain such that h and Q may be solved stably and accurately Only include necessary cross-sections: e.g. if you have a reach of drain with multiple cross-

sections of identical (or very similar) conveyance and invert level (or slope between them),

it is not necessary to include them all. Perhaps youll only need one at the start and end of

that section, (or one in the middle, for a very short section). (Note that additional Q- and h-

points will be automatically inserted during the simulation, based on the Max dx specifiedin the NWK file, such that h is solved for all along the drain, not only at the cross-sections.)

Use Processed Data option in cross-section file, check variation in Conveyance betweendifferent cross-sections

Consider an example from upstream of Singapore River:

For the first section of drain, a number of unnecessary cross-sections are present, whichcould be removed to improve the models run times. The reach also shows an example of a

cascade, where a sudden drop in the drains invert level is represented using two cross-

sections very close together. While this is physically accurate, it is not well schematise the

Q-point in between the two h-points at the cross-sections is solving for a very high slope

and is sure to become unstable at some point.

A potential solution for cascades is to model them using a Weir structure, (which solves forQ using the Energy Equation), which would more accurately account for the energy

dissipation involved.

Consider other locations throughout the model network that might be improved similarly?

Identical cross-sections, on a

constant slopedoesnt require so

many cross-sections model can bemade more efficient by simply

removing unnecessary cross-

sections

Cascade can be better

represented in other

ways, (although slope

here not too high)


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Exercise 5: Representation of structures

Culverts and road crossings: sometimes represented using cross-sections very close together, with

different cope levels. As discussed, cross-sections very close together can cause instability and will

definitely slow the model down. These may be better represented using the Culvert structure

option in the NWK file.

Cascades: as mentioned briefly, if it is important that particular cascades be included in the model,

they might be represented using weirs to model the drop in invert levels (and associated energy

dissipation).

Barrage gates: Try to include the barrage gates in the model using the Control Structures option

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