Reaches
The Reaches feature class is a line feature class that delineates the stream network. Data ("flowlines") can be imported from the National Hydrography Dataset or from data provided by a water management district, or other data source depending on the area to be simulated. The features can be imported using the Import GIS Data command. The data does not need to be clipped to the basin boundary, but reaches outside the boundary will not receive any inflows from the surrounding land. Typically, outflow reaches will extend beyond the basin boundary, and inflow reaches (if present) may also extend beyone the basin boundary.
The tools to build the stream network are discussed in greater detail later. Generally, building the stream network is the most time-consuming part of model setup. A few points to keep in mind:
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The model needs at least one outfall reach. Multiple outfall reaches can be present, but each outfall reach requires an associated stage boundary condition.
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Reaches cannot be isolated from the rest of the stream network unless it is an outfall reach and a boundary condition is assigned to it.
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During the building of the stream network, the processing tools rely on the individual line features being connected at their endpoints. Any particular reach can connect to multiple reaches at either the upstream or downstream end. Line features may overlap other line features, but the overlapping reaches will not be connected together.
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During the building of the stream network, reaches will automatically be numbered. Reaches are numbered consecutively such that there are no skipped numbers for the stream network as a whole, but a reach does not need to be attached to a reach that has a number either one higher or lower. In other words, a reach numbered 25 can be attached to a reach numbered 40 with no issues. For this reason, after the stream network is built, stream reaches should not be deleted without reassigning the number to another reach.
Data Quality Assumptions
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The spatial extent of each polyline feature is accurate and represents a hydrologic feature.
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Connected reaches share endpoints.
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Any isolated reach or group of reaches has at least one outfall reach.
The required field used by the WAM Reaches feature class is:
| Attribute | Alias | Data Type | Scenario_WAM Join Table |
|---|---|---|---|
| Calcreach | Calculation Reach | Long Integer | N/A |
| Typereach | Reach Type | String (20) | N/A |
| Typeflow | Flow Type | String (20) | N/A |
| TOB_elev | Top of Bank Elevation | Double | N/A |
| BottomElevation | Reach Bottom Elevation | Double | N/A |
| ReachGroupID | Reach Group ID | Long Integer | N/A |
| ReachName | Reach Name | String (100) | N/A |
| PriorCalcreach | PriorCalcreach | Long Integer | N/A |
| ReachTypeID | Reach Type ID | Long Integer | N/A |
Other legacy fields are present in the feature class but are unused, e.g., "Tag", "To_reach1", "To_reach2", etc. There is also a field named "PrevCalcreach" that is unused but should not be confused with the "PriorCalcreach" field.
Note that the Reaches feature class is not joined to the Reach_Type table in the Scenario_WAM database, but a dynamic join is used to populate data from the Reach_Type table in the Scenario_WAM database. This dynamic join uses the Calcreach -> Reach_Type.ID fields. Note that two other tables in the Scenario_WAM database that use values from the Calcreach field are the Reach_NextDown_Char and Reach_Profile_Char tables. These give the connectivity structure of the stream network and the cross-sectional profiles, respectively.