Design Rainfall
58.98 mm
24-hour synthetic design storm.
HEC-HMS · Technical workspace
Results
The HEC-HMS results describe the design-flood response of the 162.035 km² Hare River watershed at the Hare Weir / irrigation headworks. The current accepted reference simulation is the 50-year design event.
Current accepted result:
the 50-year, 24-hour design storm of 58.98 mm produces
an outlet peak discharge of 114.4 m³/s at
Sink-1 / Hare Weir.
1. Design Peak Summary
10-year peak
Pending
25-year peak
Pending
50-year peak
114.4 m³/s
100-year peak
Pending
| Return Period | 24-h Rainfall (mm) | Peak Q (m³/s) | Runoff Depth (mm) | Status |
|---|---|---|---|---|
| 10 years | 49.61 | — | — | Not yet finalised |
| 25 years | 54.99 | — | — | Result to be confirmed |
| 50 years | 58.98 | 114.4 | 16.84 | Completed / accepted |
| 100 years | 62.95 | — | — | Not yet finalised |
Result-control rule:
preliminary test values are not displayed as final design results.
The 10-, 25- and 100-year peak discharges will be entered only after
their final simulations have been checked and accepted.
2. Accepted 50-Year Design Result
The 50-year event is the present reference simulation for the Hare headworks reassessment. All basin geometry, loss, transform and routing settings are those documented in the final HEC-HMS model.
Peak Discharge
114.4 m³/s
Peak discharge at Sink-1 / Hare Weir.
Runoff Depth
16.84 mm
Direct runoff generated by the accepted event simulation.
Runoff Volume
≈ 2.73 million m³
Approximate basin runoff volume corresponding to the reported runoff depth over 162.035 km².
Peak Time
Simulation Day 1 · approximately 16:15
Peak occurs after the principal design-storm rainfall pulse and upstream routing response.
Model Outlet
Sink-1 / Hare Weir
Final discharge extraction point for the irrigation diversion and headworks assessment.
3. Outlet Hydrograph
The outlet hydrograph is the principal HEC-HMS result used for hydraulic design. It describes not only the maximum flow, but also the timing, duration and recession of the flood wave arriving at the Hare Weir.
50-year outlet result:
the accepted simulation reaches a peak discharge of
114.4 m³/s at approximately
16:15 on 1 January 2000 at
Sink-1 / Hare Weir.
4. Flow Contribution at the Outlet Peak
At the time of the accepted 50-year outlet peak, most of the discharge arriving at Sink-1 is routed from the upstream watershed through R_2. A smaller local contribution is added from S_4 near the downstream end of the basin model.
R_2 Routed Flow
≈ 111.1 m³/s
Routed upstream contribution arriving through reach R_2 at the time of the outlet peak.
S_4 Local Contribution
≈ 3.2 m³/s
Local runoff contribution from S_4 at approximately the same peak time.
Rounding:
the component values are reported approximately, so their rounded sum
may differ slightly from the final HEC-HMS outlet peak of 114.4 m³/s.
5. Runoff Depth and Volume
The accepted 50-year event produces a direct runoff depth of 16.84 mm. Applied across the full modelled watershed, this corresponds to approximately 2.73 million m³ of runoff volume.
Volume check
Runoff Volume = Runoff Depth × Watershed Area
0.01684 m × 162.035 × 106 m² ≈ 2.73 × 106 m³
This volume represents the storm-generated runoff simulated by the event model. Because baseflow is set to None, it should not be interpreted as the total volume of river flow that would occur during the same period in a continuous hydrologic simulation.
6. Result Elements
The following figures provide the graphical record of the adopted 50-year HEC-HMS simulation. The design-storm hyetograph is retained here as the rainfall-input reference; the remaining figures document the resulting watershed response and HEC-HMS outputs.
Input versus result:
the design-storm hyetograph is an HEC-HMS input.
The outlet hydrograph, element peak flows, runoff depth and volume, and
simulation summary are HEC-HMS results.
50-year, 24-hour rainfall distribution used by the HEC-HMS meteorologic model.
Sink-1 / Hare Weir; peak discharge 114.4 m³/s at approximately 16:15.
Global-summary peak discharge, peak timing and runoff-depth information for S_1–S_5, J_1–J_2, R_1–R_2 and Sink-1.
Comparison of peak discharge and timing across the hydrologic elements in RUN_HARE_50YR.
Outlet runoff depth 16.84 mm, corresponding to approximately 2.73 million m³ over the modelled watershed.
Consolidated 50-year simulation information, Global Summary Results, peak-flow comparison and outlet statistics.
7. Engineering Interpretation
The HEC-HMS result provides the flood hydrograph required for evaluating the hydraulic adequacy and safety of the Hare diversion structures. The design flow must be considered together with the geometry and hydraulic capacity of the weir, under-sluice, approach reach, head regulator and associated river-control works.
The accepted 50-year peak of 114.4 m³/s is therefore not treated as an isolated number. Its timing, hydrograph shape and runoff volume are also relevant to hydraulic loading and flood passage through the headworks.
Design use:
the HEC-HMS result is a hydrologic input to the hydraulic design.
Structural dimensions should not be selected from peak discharge alone;
the final design must also consider hydraulic calculations, freeboard,
sediment passage, scour, river morphology and applicable design guidance.
8. Comparison with the 1995 Study
The accepted HEC-HMS 50-year peak is compared separately with the historical 1995 Log-Pearson Type III estimate. The modern rainfall-runoff simulation gives 114.4 m³/s, whereas the historical 50-year statistical estimate was 59.183 m³/s.
The difference is retained explicitly as part of the engineering record and is discussed on the Validation & 1995 Comparison page.
9. Current Result Status
| Output | Status |
|---|---|
| 50-year rainfall input | Final — 58.98 mm / 24 h |
| 50-year peak discharge | Final — 114.4 m³/s |
| 50-year runoff depth | Final — 16.84 mm |
| 50-year runoff volume | Final — approximately 2.73 million m³ |
| 50-year peak timing | Recorded — approximately Day 1, 16:15 |
| 10-year event | Not yet finalised |
| 25-year event | Final outlet result to be confirmed |
| 100-year event | Not yet finalised |
| Graphical result elements | Completed — final figures inserted |
| SWAT comparison | Next independent hydrologic stage |
10. Result Summary
| Watershed Area | 162.035 km² |
|---|---|
| Reference Event | 50-year design storm |
| 24-hour Rainfall | 58.98 mm |
| Peak Discharge | 114.4 m³/s |
| Runoff Depth | 16.84 mm |
| Approx. Runoff Volume | 2.73 million m³ |
| Peak Time | Simulation Day 1 · approximately 16:15 |
| Outlet | Sink-1 / Hare Weir |
| Next Hydrologic Check | SWAT watershed simulation |
These results complete the present HEC-HMS design-event record for the accepted 50-year simulation. Additional return-period results and future graphical elements can be added without changing the underlying page structure.