1. Flood Management Flood Control Flood Estimation Flood Routing

2. Flood Damage

3. Flood Damage

10. Classification of floods • a) Fluvial Flooding: • from rivers and streams, including that resulting from the restricted capacity and blockage of culverts conveying watercourses; • b) Coastal Flooding: • from high tides and/or storm surges; • c) Pluvial Flooding: (sometimes known as ‘urban’ or surface water flooding) • resulting from the sensitivity and limiting capacity of the existing or proposed surface water drainage network and combined drainage systems • d) Groundwater Flooding. • man-made situations can result in unexpected and catastrophic flooding. Indicative areas of concern include reservoirs and dams,, and the inadequate capacity of culverts, particularly below embankments.

11. How are flood hazard areas regulated • Flood hazard area mapping • Limiting construction in the floodway and flood fringe • Limiting fill in the flood way and flood fringe • Placing structures above the Base flood elevation • Limiting reconstruction and additions with the floodway and flood fringe

19. Flood Forcasting • Flood fighting- emergency measures • Evacuation and shelter Management • Flood Insurance • Flood Zoning • Changing cropping pattern

29. Case Study Dahej The Snyder unit hydrograph for 100 yr-return period

30. RP: 100yr Max Depth: 0.62 mt RP: 10yr Max Depth: 0.47 mt RP: 2 yr Max Depth: 0.37 mt RP: 100yr Max Depth: 1.3 mt RP: 10yr & 100 yr Max Depth: 11.2 mt RP: 10yr Max Depth: 1.0 mt RP: 2 yr Max Depth: 5.9 mt RP: 2 yr Max Depth: 0.8 mt RP: 100yr Max Depth: 0.6 mt RP: 10yr Max Depth: 0.5 mt RP: 2 yr Max Depth: 0.4 mt (10 yr ) (100 yr ) Pluvial Flood Risk Analysis • Catastrophic inland 100yr flood is most intensive in the Dahej area with the depth of 11.2mts. • Besides the pluvial flood, anthropogenic activities have modified the slope causing water logging. Water Logged

31. Fluvial floods Longitudinal Section with water profile

32. Profile 2 at the 33975.86 Cross section X-Y-Z Perspective of the flood plain

33. Tidal & FluvialFloodRisk Analysis • Fluvial flood is calculated with cumulative effect of river and sea flow. • Fluvial flood from R.Narmada would extend into the land in the north upto 10 kms. in RP: Avg, 100 & 200yr flood. • High tide line outlines the coastal flood influence zone. RP: 200yr Max Depth: 14.26 mt RP: 100yr Max Depth: 14.19 mt RP: Avg Max Depth: 9.26 mt High tide area

34. Groundwater Flood Risk Analysis No Ground Water Flooding Water table is below sea level in Dahej area. Threat of sea water intrusion and subsequent salinity intrusion in the area if groundwater pumping is allowed in the area. “Zero” water table contour shifts towards the sea in monsoon period indicating that the artificial recharge methods would work in the area. 1 1 0 0 -1 -1 Taluka Map

35. Rainwater harvesting Reservoirs detention: At deep valleys Levees and floodwalls: Along Stream channel Channel improvements: By dredging, channelisation, diversion Flood Mitigation- Principal concepts Proposal for arresting the catchment at NH at Bharuch to be expedited Crossings and roadways: Elevated roadways Drainage and storm sewer improvements Drainage system maintenance Local Structural protection: Build-up local embankments, plant vegetation, cracks in gullies. B1 B2 C D B3 A

36. END