6.4.2. Flood Planning Area

6.4.2.Flood Planning Area

The FPL, and other flood related development controls, are applied to properties within the Flood Planning Area (FPA). The FPA is typically the land at or below the flood planning level. It is important to define the boundaries of the FPA to ensure flood related planning controls are applied where necessary and not to those lots unaffected by flood risk. It is also important to define the FPA on criteria defined in the NSW Floodplain Development Manual (Reference 5). The Urana Shire DCP 2011 notes that ‘the extent of the floodplain within Urana Shire has been determined using the Department of Water Resources Murrumbidgee Valley Floodplain Atlas “Yanco, Colombo and Billabong Creeks” [1987], and in some areas, local knowledge.” These maps broadly indicate areas subject to mainstream flooding only (not overland flow), including reaches of the main waterways between the five villages. A provisional flood planning area (FPA) map was later developed for each village as part of the Flood Study for the Towns of Urana, Morundah, Boree Creek, Oaklands and Rand (Reference 7). The Provisional FPA was based on the extent of the 1% AEP event plus 0.3 m freeboard, trimmed to the PMF extent. Due to the relatively flat terrain in each village, this tends to result in the FPA covering approximately the same extent as the PMF. This is a conservative approach that encompasses properties that may not be subject to flood risk in events more frequent than the PMF, and can lead to development controls being applied where they are not warranted. This can make development applications (and their assessment by Council) overly onerous, and in some cases, prevent appropriate developments from being approved within the floodplain. This FRMS&P provides an opportunity to assess the suitability of this approach, particularly in areas subject to shallow overland flow affectation. Whilst there is an opportunity to vary the FPA based on the source of flooding (that is differentiate mainstream and overland flow) this does create further potential confusion. As such, it was agreed with Council that the FPA would be defined based on mainstream flooding (which encompasses overland flow areas). 6.4.2.1. Determine Mainstream FPA Following the freeboard selection described in Section 6.4.1.2, a freeboard of 0.3 m was added to the peak 1% AEP flood level and the resulting level was extended laterally (“stretched”) on either side of the channel or creek, to intersect with the ground (using topographic data) (Figure Figure 4. This approximates the extent of a flood that is 0.3 m higher than the 1% AEP flood, and forms the boundary of the mainstream FPA. The Mainstream FPA therefore represents the area beneath the Mainstream Flood Planning Level, as defined in Section 6.4.1.3. DRAFT FOR PUBLIC EXHIBITION