Hydrology Suite · SSK Enviro

💧

Hydrology

South Africa's most comprehensive water intelligence toolkit. Built on NWA, NEMA and SANS standards — designed for Environmental Assessment Practitioners, engineers and planners.

🌊 Flood Risk Assessment

1:10 to 1:100 year return periods, NEMA triggers

🏔 Catchment Delineation

WMA, catchment area, flow accumulation

🌧 Stormwater Calculator

Rational method, SCS-CN, detention sizing

〰 Watercourse Delineation

Floodlines, riparian buffers, NWA S21

🌿 Wetland Screening

HGM, PES rating, EIA triggers, offsets

Flood Risk Assessment

Return period flood risk analysis aligned to SANS 10400-Q and NEMA GN R326/327. Determines 1:10, 1:50 and 1:100 year floodlines and EIA triggers.

Site

Catchment

Results

Site Location

Latitude (DD)

Longitude (DD)

Province

Watercourse / River Name (if known)

Catchment Parameters

Catchment Area (km²)

If unknown, use Catchment Delineation tool first

Mean Annual Precipitation (MAP) — mm

700mm

Catchment Slope — %

2.5%

Land Use & Soil

Dominant Land Use

Soil Hydrological Group

Analysis Settings

Return Periods

1:10 year 1:50 year 1:100 year 1:200 year

Climate Change Adjustment

CSIR GreenBook recommends +20% for 2050 design in most of SA

Summary

Peak Flows

Legal

Map

1:100 Year Peak Flow

—

m³/s

1:50 Year Peak Flow

—

m³/s

1:10 Year Peak Flow

—

m³/s

Flood Risk Rating

—

Overall

Peak Flow by Return Period (m³/s)

Return Period	Peak Flow (m³/s)	+CC Adjustment	Flood Volume (Mm³)

Lat —Lng —Zoom 6

Hover for coords

Catchment Delineation

Delineate upstream catchment area, identify the Water Management Area (WMA), sub-catchment and flow characteristics. Essential for NWA Water Use Licence applications.

Pour Point (Outlet)

Latitude

Longitude

Province

Catchment Characteristics

Terrain Type

Dominant Geology

Mean Annual Runoff (MAR) — Mm³/year (if known)

Leave blank to estimate from MAP and catchment characteristics

WMA Identification

Nearest Major River

Estimated Catchment Size

Summary

Hydrology

WMA / Legal

Map

Run the analysis to see catchment results

Lat —Lng —Zoom 6

Hover for coords

Stormwater Calculator

Peak runoff using the Rational Method and SCS Curve Number method. Detention pond sizing, outlet design and SANS 10400-S compliance assessment.

Calculation Method

Rational Method

Catchment area <25 km² · SANS 10400-S

SCS Curve Number

Any size · accounts for antecedent moisture

Both Methods + Comparison

Best practice — use higher of two results

Site Parameters

Drainage Area (ha)

Return Period

Rainfall Region (SA Zone)

Average Slope (%)

Surface Characteristics

Runoff Coefficient (C) — or select land use

SCS Curve Number (CN)

CN 75

CN 40=forest, 60=grass, 75=crops, 85=urban, 98=impervious

Detention / Retention Design

Pre-development vs Post-development

Post-development Imperviousness (%)

55%

Results

Detention

Hydrograph

SANS Compliance

Enter parameters and run calculation

Synthetic Unit Hydrograph

Watercourse Delineation

Identify watercourse presence, delineate 1:10 year floodline, riparian buffer zones and determine NWA Section 21 water use triggers for your development.

Site Details

Latitude

Longitude

Watercourse Type

Channel Width (m) at bankfull

Channel Depth (m) at bankfull

Channel Bed Slope (%)

1.5%

Channel Manning's n (roughness)

Development Context

Development Activity

Distance from watercourse edge (m)

Summary

Buffer Zones

NWA S21

Map

Enter parameters and delineate

Lat —Lng —Zoom 6

Hover for coords

Wetland Screening Tool

Hydrogeomorphic (HGM) wetland classification, Present Ecological State (PES) rating, NEMA EIA trigger determination and ecological offset estimation.

Wetland Location

Latitude

Longitude

Province / Biome

Estimated Wetland Area (ha)

HGM Classification

Wetland Type (HGM)

Vegetation Cover

Ecological Condition (PES)

Hydrology — How altered is the water regime?

Geomorphology — Physical structure

Invasive Alien Plants (IAP) Cover

Impact Assessment

Proposed Activity

Proposed Impact Area (ha)

Any loss of wetland >0.5 ha typically triggers NEMA Basic Assessment

PES Rating

EIA Triggers

Offset Calc

Map

Enter wetland details and run screening

Lat —Lng —Zoom 6

Hover for coords