# Unit Hydrograph Data Fields (SWMM)

Unit Hydrographs in SWMM networks are used to determine RDII (Rainfall Derived Infiltration and Inflow) entering the system.

Information relating to a unit hydrograph can be viewed and edited on the Unit Hydrograph Grid Window of the Nodes Grid or on the Unit Hydrograph Property Sheet.

The table below describes all the data which can be used to define a unit hydrograph.

Fields that are common to the majority of objects can be found in the Common Fields topic.

## Unit Hydrograph Data

Database Table Name: sw_unit_hydrograph

Field Name |
Help Text |
Database Field |
Size |
Precision |
Default |
Error Lower Limit |
Error Upper Limit |
Warning Lower Limit |
Warning Upper Limit |
||
---|---|---|---|---|---|---|---|---|---|---|---|

UH group | The name of the Unit Hydrograph Group that this Unit Hydrograph is part of. | group_id | Text | 254 | 0 | ||||||

Month |
The month that applies to this unit hydrograph can be selected from a dropdown list. Selecting ALL will apply the Unit Hydrograph to every month. |
month | Text | 4 | 0 | ALL | |||||

Response ratio R - short term | The area under the graph representing the proportion of rainfall entering the drainage network for the short-term rainfall response component of hydrograph. | R1 | Double | 3 | 0 | 0 | 1 | ||||

Time to peak T - short term | Time from the onset of rainfall to the peak of the triangle of the graph for the short-term rainfall response component of hydrograph. | T1 | Double | Hours | 3 | 0 | |||||

Recession limb ratio k - short term | Ratio of 'time to recession' to the 'time to peak' of the graph for the short-term rainfall response component of hydrograph. | K1 | Double | 3 | 0 | 0 | 1 | ||||

Response ratio R - medium term | The area under the graph representing the proportion of rainfall entering the drainage network for the medium-term rainfall response component of hydrograph. | R2 | Double | 3 | 0 | 0 | 1 | ||||

Time to peak T - medium term | Time from the onset of rainfall to the peak of the triangle of the graph for the medium-term rainfall response component of hydrograph. | T2 | Double | Hours | 3 | 0 | |||||

Recession limb ratio k - medium term | Ratio of 'time to recession' to the 'time to peak' of the graph for the medium-term rainfall response component of hydrograph. | K2 | Double | 3 | 0 | 0 | 1 | ||||

Response ratio R - long term | The area under the graph representing the proportion of rainfall entering the drainage network for the long-term rainfall response component of hydrograph. | R3 | Double | 3 | 0 | 0 | 1 | ||||

Time to peak T - long term | Time from the onset of rainfall to the peak of the triangle of the graph for the long-term rainfall response component of hydrograph. | T3 | Double | Hours | 3 | 0 | |||||

Recession limb ratio k - long term | Ratio of 'time to recession' to the 'time to peak' of the graph for the long-term rainfall response component of hydrograph. | K3 | Double | 3 | 0 | 0 | 1 | ||||

Max initial abstraction rainfall depth -short term | Maximum initial abstraction rainfall depth for the short-term rainfall response component of hydrograph. | Dmax1 | Double | RD | 3 | 0 | 0 | ||||

Initial abstraction recovery rate - short term | Initial abstraction recovery rate for the short-term rainfall response component of hydrograph. | Drec1 | Double | RD | 3 | 0 | 0 | ||||

Initial abstraction depth - short term | Initial abstraction rainfall depth for the short-term rainfall response component of hydrograph. | D01 | Double | RD | 3 | 0 | 0 | ||||

Max initial abstraction rainfall depth -medium term | Maximum initial abstraction rainfall depth for the medium-term rainfall response component of hydrograph. | Dmax2 | Double | RD | 3 | 0 | 0 | ||||

Initial abstraction recovery rate - medium term | Initial abstraction recovery rate for the medium-term rainfall response component of hydrograph. | Drec2 | Double | RD | 3 | 0 | 0 | ||||

Initial abstraction depth - medium term | Initial abstraction rainfall depth for the medium-term rainfall response component of hydrograph. | D02 | Double | RD | 3 | 0 | 0 | ||||

Max initial abstraction rainfall depth -long term | Maximum initial abstraction rainfall depth for the long-term rainfall response component of hydrograph. | Dmax3 | Double | RD | 3 | 0 | 0 | ||||

Initial abstraction recovery rate - long term | Initial abstraction recovery rate for the long-term rainfall response component of hydrograph. | Drec3 | Double | RD | 3 | 0 | 0 | ||||

Initial abstraction depth - long term | Initial abstraction rainfall depth for the long-term rainfall response component of hydrograph. | D03 | Double | RD | 3 | 0 | 0 |