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Applied Hydrology RSLAB-NTU Lab for Remote Sensing Hydrology and Spatial Modeling 1 Flood Routing & Detention Basin Design Professor Ke-Sheng Cheng Dept.

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Presentation on theme: "Applied Hydrology RSLAB-NTU Lab for Remote Sensing Hydrology and Spatial Modeling 1 Flood Routing & Detention Basin Design Professor Ke-Sheng Cheng Dept."— Presentation transcript:

1 Applied Hydrology RSLAB-NTU Lab for Remote Sensing Hydrology and Spatial Modeling 1 Flood Routing & Detention Basin Design Professor Ke-Sheng Cheng Dept. of Bioenvironmental Systems Engineering National Taiwan University

2 Lab for Remote Sensing Hydrology and Spatial Modeling RSLAB-NTU 2 The storage effect The storage effect of a water-retention structure or a channel reach can change the shape of the inflow hydrograph. Therefore two types of routing procedures are needed to calculate the outflow hydrograph. Level-pool routing Channel routing

3 Lab for Remote Sensing Hydrology and Spatial Modeling RSLAB-NTU 3 Level-Pool Routing (Reservoir Routing) For a reservoir the outflow is uniquely controlled by the water depth (or stage) of the reservoir pool. Also, the reservoir storage is a single-value function of the stage. Flow velocity in the reservoir is usually very low.

4 Lab for Remote Sensing Hydrology and Spatial Modeling RSLAB-NTU 4 Comparison of flow routing under invariable and variable stage-discharge relationships Invariable S~Q relationshipVariable S~Q relationship

5 Lab for Remote Sensing Hydrology and Spatial Modeling RSLAB-NTU 5 Discharge under variable S~Q relationship

6 Lab for Remote Sensing Hydrology and Spatial Modeling RSLAB-NTU 6 Reservoir routing Modified puls method (Storage indication method)

7 Lab for Remote Sensing Hydrology and Spatial Modeling RSLAB-NTU 7 +

8 Lab for Remote Sensing Hydrology and Spatial Modeling RSLAB-NTU 8

9 Lab for Remote Sensing Hydrology and Spatial Modeling RSLAB-NTU 9 An example Given the following storage-outflow relationship and inflow hydrograph, calculate the outflow hydrograph. (Use 10- minute routing interval).

10 Lab for Remote Sensing Hydrology and Spatial Modeling RSLAB-NTU 10 Stage~storage~outflow relationship

11 Lab for Remote Sensing Hydrology and Spatial Modeling RSLAB-NTU 11

12 Lab for Remote Sensing Hydrology and Spatial Modeling RSLAB-NTU 12 Reservoir routing as a computation of mass balance For a reservoir the outflow is uniquely controlled by the water depth (or stage) of the reservoir pool. Also, the reservoir storage is a single-value function of the stage. As a result, given a stage the reservoir storage and outflow can be uniquely determined, if the stage~storage and stage~outflow relationships are known. An intuitive trial-and-error approach for reservoir routing can be implemented.

13 Lab for Remote Sensing Hydrology and Spatial Modeling RSLAB-NTU 13 Alternative solution Stage~storage Stage~discharge

14 Lab for Remote Sensing Hydrology and Spatial Modeling RSLAB-NTU 14 Spreadsheet calculation

15 Lab for Remote Sensing Hydrology and Spatial Modeling RSLAB-NTU 15 Inflow-outflow-(10*storage)

16 Lab for Remote Sensing Hydrology and Spatial Modeling RSLAB-NTU 16 Channel routing


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