LA RIERETA

1. LA RIERETA MODELING AND SOLUTIONS FOR FLOODING PROBLEMS USING SWMM 5.0

2. PRESENTATION This work is under a bigger perspective witch the objective is to solve urban drainage problems at La Riereta Basin . This basin suffers from flooding events mainly due to the impermeability of its ground. Many measures will be proposed from different aspects of urban drainage theories but, all of them are going to be based on modeling using SWMM 5.0.

3. La Riereta is an urban basin located at one of the most urban areas in Barcelona called San Boi de Llobregat. The basin is reported to have high slopes an there are hardly any green areas inside its limits. The aproximate area of La Riereta is 18 ha and there are register of 80 cm near its outfall due to flood. DESCRIPTION Source: Grupo Flumen UPC

4. LA RIERETA OUTFALL

5. DISCRETIZATION The basin’s drainage was defined by analyzing a topographic map witch presents the streets heights, pipes heights and direction of flow identifying its patterns. This is a very important step to develop the modeling correctly and to get the diagnosis. To get the discretization the basin’s limits were designed considering the areas that are responsible to contribute with flow to the outflow point.

6. DISCRETIZATION The same idea was applied to select the sub-basins. For each area that supposed to be one sub-basin, an identification of its pipes was made and if these pipes contributes to the discharge of the basin, then it was consider one sub-basin. If the sub-basin has more than one pipe that contributes to the basin’s discharge, the pattern assumed is that the flow goes to the pipe with the biggest slope. The final topologic design contains 13 sub-basins and are showed below:

7. DISCRETIZATION OUTFALL

8. The area located between Francesc Macia, Viuda Vives, Cerdanya y Mallorca streets (sub-cuenca LR004) is not supposed to be included at the basin by considering all the criterions explained, but this area is reported to contribute to La Riereta. DISCRETIZATION Calle Cerdanya Calle Malorca Source: Googlemaps

9. DISCRETIZATION The drainage network is conformed by a major drainage sewer, placed at Calle de Torre Figueres – Calle de Jaume – Calle de la Rutula, starting at Calle Mossen Cinto Verdaguer and discharging at the control point. In addition, has been considered a secondary sewer placed in Calle de Francesc Macia, that receives conduit contributions from Calle del Pintor Fortuny.

10. MODELING WITH SWMM With the topologic schema defined, SWMM EPA model has been implemented, including subcatchment, nodes, conduits and information of its dimensions. From the available information the requested variables and parameters were defined : areas, wides, mean of slopes surface, impermeability percentage, roughness coefficients and storage depth for impermeable and permeable areas, infiltration model parameters, invert elevation and depth, diameters and conduits dimension’s, and manning coefficients for conduits. In the same way, the average slope of the sub-basins was determined. Width was determinate considering the contribution length for each sub-basin, between the basin head and outfall, following the consolidated drainage pattern.

11. PRE-CALIBRATION RESULTS With the first modeling, the observed and modeled volume difference were defined, using the curve number (CN) method and a constant rainfall abstraction. The following graphs shows the hydrograph using the CN method and a 3 mm/hr constant rainfall loss: HYDROGRAPHS FOR ELIAS RAINFALL EVENT DISCHARGE (m3/s) Time (min)

12. PRE-CALIBRATION RESULTS HYDROGRAPHS FOR EFREN RAINFALL EVENT HYDROGRAPHS FOR FIDEL RAINFALL EVENT DISCHARGE (m3/s) DISCHARGE (m3/s) Time (min) Time (min)

13. CALIBRATION First Efren and Elias rainfall events were chosen for calibration and Fidel was elected for Validation. It was made because these two first rainfalls presents only one peak while Fidel shows doble-peak and the 3 of them have the same amount as well.

14. CALIBRATION

15. CALIBRATION The first run was made containing the geometric parameters measured and coefficients recommended by the bibliography for this kind of scenario. It wasn’t possible to simulate correctly and simultaneously, hydrographs shapes, peak of discharges and neither the correct time that all these processes happen.

16. CALIBRATION So, the strategy was changed. Only Efren rainfall event was chosen for calibration with a constant and linear loss model. This model is able to well simulate the volume of flow generated. To calibrate the biggest discharge and the time that it happens, the width’s intake of the basin, roughness and parameters from the impermeable areas and conduits were varied until to get a similar profile with de real scenario.

17. CALIBRATION These are the final calibration parameters:

18. VALIDATION From the calibration of Efren rainfall event, Fidel was validated. So, the result is that Fidel well reproduces values like volume, discharge and time to reach the peak.

19. VALIDATION It wasn’t possible to get similar values of discharges and volumes between the reality observed and modeled, from Elias rainfall event. But the hydrographs and the time of both discharge’s peak were reproduced.

20. DIAGNOSIS There was a simulation configured with a 10 years rainfall’s return period and 1 hour of duration. The diagnosis rainfall is the 10 years return period for La Riereta Basin, and it was obtained from the Barcelona’s IDF curves. For modeling, it was assumed junction pond allowed, with an pond area 500 m2.

21. DIAGNOSIS The diagnosis indicates a leak capacity in the network, mainly in conduits placed in the basin’s highland. The worst problems are produced in: • Francesc Macia – Cerdanya • Francesc Macia – Fortuny • Mossen Verdaguer – Fortuny • Jaume – Fabra • Baldiry Comas – Jaume Collel • Luis Pascual – Pere de Riera

22. DIAGNOSIS

23. SOLUTIONS PROPOSED The proposal solution is to locate new storage units in the La Riereta Basin focusing the modeling flooded nodes. The storages units will reduces peak flow, avoiding the La Riereta flood problems for 10 years return period.

24. LR012 LR013 LR009 LR010 LR005 LR007 LR008 LR006 LR002 LR003 LR004 LR001 SOLUTIONS PROPOSED

25. SOLUTIONS PROPOSED

26. CONCLUSION • An solution for the La Riereta Basin based in storage unit on-line and off-line design has been presented. With a very restrictive space for solutions, some of these storage units can be placed under the streets, avoiding flood damages for community and infraestrucure. • An area under the 2% basin used for temporal storage can be enough for a stormwater solution, and if this is planned before urbanization would save big and costly drainage networks. • The storage based solution is an effective solution, and the surface used to storage must to be studied in location and size. Even, could be the lower cost solution for a completely developed city.

27. CONCLUSION • The proposed storage system can be optimized, using more field information and using more time for alternative analysis. • The optimal solution for La Riereta Basin must be an storage units construction combined with upper network size and slope improvement. • SWMM 5 is a very intuitive and usable tool for urban runoff modeling, even without all the information desired. • The calibration process requires experience into determinate parameters like Width and Manning roughness.