This document provides a comprehensive framework for At-Site Flood Frequency Analysis and Regional Flood Methods within the Australian context. It outlines advanced statistical techniques, such as Bayesian inference and L-moments, which allow engineers to estimate design floods by fitting data to various probability distributions. The text highlights the use of TUFLOW Flike software to manage complex tasks like censoring low-flow outliers and incorporating historical records. Additionally, it details a Regional Flood Frequency Estimation (RFFE) model developed for ungauged catchments using Generalised Least Squares regression across different geographic zones. The guidance emphasises that while standardised procedures are provide ...