Evaluating Capability of Green Stormwater Infrastructure on Large Properties toward Adaptive Flood Mitigation: The HLCA+C Methodology
Round 1
Reviewer 1 Report
Comments for author File: 
Comments.pdf
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 2 Report
The paper describes and adaptive planning methodology for flood mitigation (HLCA+C) which incorporates climate change effects on runoff volumes from drained areas and in-ground storage capacity (resulting in a flood mitigation capability for present and future climate). An FCM classification system is included for identification of SWM zones to identify GSI implementation approaches. The methodology is tailormade for adaptation which consider 'large properties' located in low-lying cities also exposed to sea level rise.
I think the paper is very well written, and supported with high quality illustrations. I have some minor comments (please check the attached pdf with marked comments). Most of the comments has a character which can be solved with 'minor revision'. However, I also have a few more general, or critical comments (also marked on the pdf).
Q1: The pincer effect (line 28). I have an intuitive understanding, but I would recommend to add a couple of references and a short explanation the first time (line 28) that this effect is used in the paper.
Q2: Actually, the pincer effect, as I understand it means that the whole system (the freshwater cycle, groundwater level, river runoff, soil moisture, storm surge etc.) with climate change will/or could change systematically, whereby e.g. groundwater levels and river runoff need to be projected based on 30-year (or more) time series, where also the storage terms in groundwater, soil and river systems are included in the modelling (which is not represented well with 'rainfall intensity' (or rain series), without also considering the 'duration' of such events. To which extent does such uncertainties (or complexities) impact the results for a city like Christchurch? (would it be possible to use rain series of several days of duration, in order to properly evaluate the storage capacity in situations of long periods with rain). Do the proposed approach underestimate the storage capacity of such events in present or only in a future climate?
Q3: In which distance from the sea is it acceptable not to include effects of storm surge on groundwater levels?
Q4: In many areas of the world, the groundwater level fluctuates due to variations in climate and other factors. Groundwater level can also increase due to increased 'winter precipitation resulting in increased groundwater recharge'. Only sea level rise is considered in the paper, eventually add a section in the discussion explaining that increased groundwater level due to other natural or man made impacts (than sea level rise) is not included in the methodology. Or would it be possible to use physical based groundwater-surface water numerical model with the proposed methodology (MIKE SHE/MIKE HYDRO or MODFLOW and similar)?
Q5: The applied separation distance (>60cm) how has that been established?
Q6: Why are hydrology based methodologies limited to 2030-2070 (line 442-444?
Q7: The HLCA+C methodology is designed for evaluating large properties that are identified as having the potential to provide substantial flood mitigation (and for max flood mitigation). This is about suitability of GSI etc. which is described in line 485-492. Are there any potential damage costs related to a possible increased infiltration into sewage systems due to the use of groundwater storage capacity, and which geological settings are the most applicable? (e.g. for Christchurch).
Comments for author File: Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
