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Services  /  Watershed Analysis
Service 07

Watershed Analysis
Understanding upstream first.

Comprehensive catchment characterisation and drainage network analysis — mapping how water flows, accumulates, and reaches your site from the entire upstream area, using GIS and industry-standard hydrological tools.

Catchment delineationDEM analysisFlow pathsQGIS/ArcGISSub-catchments7–14 days
At a glance
7–14 days
Standard delivery
DEM
Delineation method
GIS
Deliverable format
Every study includes
  • Catchment delineation & sub-catchment boundary mapping
  • Drainage network — flow paths, stream orders, confluences
  • Land use, soil type & infiltration characterisation
  • Runoff volume estimation & peak flow routing
  • Named engineer · Post-delivery support
QGIS/ArcGIS
Primary GIS tool
DEM-based
Delineation method
HEC-HMS
Runoff modelling
7–14 days
Delivery
What it is

Watershed Analysis — what HYDRisk delivers.

A watershed analysis defines the hydrological boundaries of a catchment — identifying the full upstream area that contributes runoff to a given point, and mapping the drainage network that channels that water. It is the spatial and physical foundation on which all hydrological modelling, flood risk assessment and drainage design is built.

Without a proper watershed analysis, it is impossible to correctly estimate how much water will arrive at a site during a storm event, or to design drainage infrastructure that can handle it. Undersized drainage, poorly located detention basins, and missed upstream tributaries are the most common consequences of skipping this step.

HYDRisk watershed analyses use high-resolution DEM data — SRTM, NASADEM, or LiDAR where available — processed through QGIS and ArcGIS to produce accurate, GIS-format catchment boundary maps, combined with land use and soil characterisation to derive runoff curve numbers.

The output is a complete hydrological characterisation of the upstream catchment — delivered in GIS format for direct integration with hydraulic models, drainage designs, and flood risk assessments.

Why watershed analysis matters
“You cannot design for water you have not measured — and you cannot measure it without first mapping where it comes from.”
DEM-based — not manually drawn boundaries
Full sub-catchment & stream network mapping
Land use & soil-derived curve numbers included
GIS format — direct model integration
Why it matters

Four reasons this service is critical to your project.

Understanding what this study delivers — and what happens without it — is the fastest way to evaluate whether your project needs it.

Incorrect boundaries underestimate runoff volumes
If the upstream catchment is not correctly defined, runoff volumes are underestimated — leading to undersized drainage and structural damage. A DEM-based analysis eliminates this error.
Missed tributaries cause unexpected flooding
Sites appearing low-risk locally may receive concentrated runoff from large upstream catchments through channels invisible in standard mapping.
Land use change upstream alters flood risk downstream
Deforestation, urbanisation and agricultural expansion alter runoff characteristics. A watershed analysis quantifies this impact so infrastructure can be sized accordingly.
Multi-basin sites need sub-catchment precision
Large or complex sites often span several sub-basins with different flow characteristics — treating them as one catchment masks localised risk.
What we deliver

Specific deliverables — not vague promises.

Every HYDRisk study produces a defined set of technical outputs — here is exactly what you receive.

Technical analysis outputs
  • Catchment delineation — DEM-based, GIS polygon boundary
  • Sub-catchment delineation for multi-basin sites
  • Stream network mapping — flow paths, orders, bifurcations
  • Flow accumulation & drainage direction raster analysis
  • Land use and soil characterisation — SCS Curve Number derivation
  • Runoff volume estimation and peak flow routing
GIS & report deliverables
  • Watershed analysis report — methodology, data, results
  • Catchment boundary map — GIS Shapefile and GeoTIFF
  • Sub-catchment boundaries — all sub-basins mapped and labelled
  • Stream network GIS layer — flow paths, orders, confluences
  • Land use and soil type maps — SCS CN values per sub-catchment
  • Runoff curve number table — all sub-catchments
GIS deliverables: All spatial data in Shapefile and GeoTIFF. AutoCAD DXF on request. Coordinate reference system matched to project requirements.
Request a scope →
Tools & methodology

Industry-standard tools. Region-specific data.

Every tool we use is the same software trusted by government agencies, major engineering firms and regulatory bodies worldwide.

QGIS / ArcGIS
Open Source / Esri
Primary GIS platform for DEM processing, watershed delineation, stream network extraction and spatial data production.
DEM processingStream network
HEC-HMS
US Army Corps of Engineers
Hydrological modelling for runoff volume estimation, peak discharge and hydrograph generation from watershed data.
Runoff volumesHydrographs
SRTM / NASADEM / LiDAR
NASA / Survey
High-resolution DEM data for accurate watershed delineation, scaled to project precision requirements.
Terrain dataHigh-res DEM

Step-by-step methodology

Step 01
DEM data acquisition
SRTM, NASADEM, or LiDAR DEM sourcing and pre-processing — void filling, projection, resolution assessment.
Step 02
Watershed delineation
DEM-based flow direction and accumulation analysis. Catchment boundary at project outlet. Sub-catchment division.
Step 03
Stream network extraction
Flow accumulation-based stream extraction. Stream ordering. Identification of all tributaries and confluences.
Step 04
Land use & soil characterisation
Land use classification from satellite imagery. Soil type mapping. SCS Curve Number derivation for all sub-catchments.
Step 05
Runoff estimation
Peak discharge and runoff volume calculation for all design storms. Hydrograph generation where required.
Step 06
GIS & report deliverables
Watershed report, GIS catchment/sub-catchment/stream data, runoff summary table, DEM-derived slope and flow maps.
Regional applicability

Calibrated for your region and regulatory framework.

Methodology, data sources and regulatory requirements differ between geographies. HYDRisk delivers the right approach for every region.

United States — Primary market
NOAA-based methodology
USGS DEM/NHD data, NOAA rainfall, FEMA-aligned catchment characterisation.
Regulatory frameworks
FEMA NFIPUSACE
  • USGS National Hydrography Dataset integration
  • NOAA rainfall for runoff estimation
  • FEMA-aligned catchment documentation
Middle East & GCC
GCC-specific methodology
Arid catchment delineation, wadi drainage network mapping, desert soil characterisation.
Regulatory frameworks
UAE MunicipalityAshghal (Qatar)
  • Wadi drainage network delineation from high-res DEM
  • Desert soil infiltration characterisation
  • UAE, Saudi Arabia, Qatar, Oman coverage
International
Global DEM methodology
SRTM/NASADEM global coverage, ERA5 climate context, IFC-aligned documentation.
Regulatory frameworks
IFC PS1 & PS4Equator Principles
  • Global SRTM/NASADEM coverage — any geography
  • IFC-aligned catchment documentation
  • Remote delivery — any geography covered
Related services

Services often commissioned alongside this study.

Service 04
Hydrological Studies
Watershed analysis is the spatial foundation for all hydrological modelling — often procured as a combined package.
View service →
Service 01
Flood Risk Assessment
Catchment characterisation from watershed analysis feeds directly into the FRA hydrological modelling.
View service →
Service 10
River Health Index
Watershed analysis is a core component of river health index assessment — defining study boundary and sub-basin structure.
View service →

Ready to commission a watershed analysis?

Tell us your project site and catchment context. We will scope the study and have a fixed-fee proposal within 24 hours.

Get a free consultation →
Proposal within 24hFixed-fee pricingNo obligation