MODELLING SMALL CATCHMENT AND RISKS Habib Ahsan Riley

MODELLING SMALL CATCHMENT AND RISKS Habib Ahsan Riley Consultants Ltd GEOTECHNICAL ENVIRONMENTAL March 2019 CIVIL WATER RESOURCES

PRESENTATION TOPICS Ø What is Small Catchment? Ø Large vs Small Catchment Ø What are the possible Risks? Ø Factors Contributing Risks? Ø Case Studies Ø Conclusions Ø Questions and Answers Habib Ahsan Riley Consultants Ltd GEOTECHNICAL ENVIRONMENTAL March 2019 CIVIL WATER RESOURCES

WHAT ARE SMALL CATCHMENT/PROJECTS Ø Private Owner Ø Private Developer Ø Small Development GEOTECHNICAL ENVIRONMENTAL CIVIL WATER RESOURCES

LARGE vs SMALL CATCHMENT Large Catchment Small Catchment Council Owned Private Owner Planning Leads to Data Collection No Planning – No Data Gathering Usually Plenty of Time Rushing Usually no Budget Issue Small Fee Consider Receiving Environment Ignore Receiving Environment GEOTECHNICAL ENVIRONMENTAL CIVIL WATER RESOURCES

GENERAL FACTORS CONTRIBUTING RISKS Ø Receiving Environment Ø Inflow/Spills from Upper Catchment Ø Downstream Boundary Condition v. River is the Downstream Boundary v. Additional Inflow at Downstream v. Inaccurate Boundary Condition Ø Missing Structures v. Missing major Culverts/ Bridges v. Missing Stop Bank Information GEOTECHNICAL ENVIRONMENTAL CIVIL WATER RESOURCES

OTHER CONTRIBUTING FACTORS FOR RISKS Ø $- Value Ø Rushing Ø Inexperience/Lack of Guidance to Modeller GEOTECHNICAL ENVIRONMENTAL CIVIL WATER RESOURCES

CASE STUDY - CASE 1 GEOTECHNICAL ENVIRONMENTAL CIVIL WATER RESOURCES

CASE STUDY - CASE 2 GEOTECHNICAL ENVIRONMENTAL CIVIL WATER RESOURCES

CASE STUDY - CASE 3 GEOTECHNICAL ENVIRONMENTAL CIVIL WATER RESOURCES

CASE STUDY - CASE 4 GEOTECHNICAL ENVIRONMENTAL CIVIL WATER RESOURCES

CASE STUDY - CASE 5 GEOTECHNICAL ENVIRONMENTAL CIVIL WATER RESOURCES

RISKS & CONSEQUENCES Risks Ø Inaccurate Assessment Ø May Affect Receiving Environment Consequences Ø Client may not accept the Results Ø Repetition of Works Ø Delays in Program GEOTECHNICAL ENVIRONMENTAL CIVIL WATER RESOURCES

CONCLUSIONS /SUGGESTIONS Ø Use Available Wider Catchment Model Ø Accurately Define Catchment Boundary Ø Use Council GIS Database to Identify any Major Structure Ø Use Google Street View to identify Culverts/Bridges Ø Identify inflows/Spills from Upper Catchment Ø Identify Impact of any River flow Ø Establish Boundary Condition Ø Extent Downstream Boundary away from Point of Interest Ø Communicate with Client about Data Requirements and Consequences GEOTECHNICAL ENVIRONMENTAL CIVIL WATER RESOURCES