Tasman District Council

Source Documents

These are the council documents used to build the TDC calculator. If a link is broken, the document may have moved on the council website.

Calculation Methodology

Method: Rational Method (NTLDM)

Tasman shares the Nelson Tasman Land Development Manual with Nelson City Council. Post-development peak flows for 10yr, 20yr, and 100yr ARI must not exceed pre-development at critical downstream locations. On-site tanks: lower 2/3 for reuse, upper 1/3 for detention.

Design Requirements

• 10yr, 20yr, 100yr ARI - post-dev <= pre-dev at critical downstream
• 1% AEP floodway design
• Rational Method: Q = C x I x A x 2.78 (L/s)
• C values from NTLDM Table 7-4 with slope correction
• On-site tanks: 2/3 reuse (lower), 1/3 detention (upper)
• Extended detention: 24hr drawdown
• CPEng certification required for detention basins/dams
• Consent notice (RMA s221) on property title

Submission

Required Documents

• Catchment plan and hydrological analysis
• Detention sizing for 10yr, 20yr, 100yr ARI
• Resource consent copies
• Maintenance plan
• CPEng design certificate (basins/dams)
• Manufacturer's tank specifications

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