Urban Development Directorate, Government of the People’s Republic of BangladeshMymensingh Strategic Development Plan Project, 2011-2031

Guidelines for Stormwater Drainage Analysis and Design

Dr. M. Shah Alam KhanProfessor

Institute of Water and Flood Management, BUET

CIRDAP Auditorium, Dhaka11 May 2014

Learning from Dhaka

• Diminished stormwater detention areas and natural water bodies: consequences on urban flooding

• Empoldering and pumped drainage: a challenging task • Domestic wastewater in storm sewers• Box Culvert: A sediment trap!• Deferred maintenance: O&M financing• Institutional arrangement: who does what?

Basic Principles

• Detention-based gravity drainage as much as possible- contingency/temporary pumping only when required

• Separate or combined systems for stormwater and domestic wastewater drainage ?

• Operation and Maintenance embedded in the activities of the local government; adequate funds in the annual budget

Major Activities

• Identify land use characteristics based on planned development in different areas: Consequence on storm runoff

• Identify water bodies and drainage network (natural and constructed): Protect those now than later

• Determine ground elevations for future development in different areas

• Design stormwater drainage system (drainage network, detention areas, drainage management structures: sluice gates, regulators, embankments, temporary pumping, etc.)

Methodologies and Data

A. Hydrological Analysis: WL and rainfall at different frequencies: tidal water level

data, daily rainfall data, hourly rainfall data

B. Flood Risk Assessment: • External (river) flooding: topographic data and DEM,

inundation maps• Internal (stormwater) drainage/flooding: identify sub-

catchments, assign runoff coefficients based on future land use characteristics, projected design rainfall considering cc trend, estimate catchment runoff and sewer discharge

Methodologies and Data

C. Design of Stormwater Drainage System Components:storm sewer network, detention areas, water control structures, etc.: IDF curves and design rainfall- synthetic hourly rainfall data

D. Performance Evaluation of the Proposed System: numerical models, e.g., SWMM, MOUSE, etc.,

topographic data and DEM, assessment of storm runoff quality based on improved solid waste management

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