Rainfall · Space · Flooding

inches of liquid water per month · A single-station value. The station sits inside Cambridge, at the coordinates the same query returns, but one gauge does not describe a whole city and rainfall varies across it. An individual month departs from its normal substantially in both directions. NOAA publishes no interval or standard deviation alongside this dataType, so none is shown.

inches of liquid water per year · Same single-station caveat as T02-M01. A normal year is not next year: the figure describes the average of a thirty-year period that has ended, and carries no information about any future year. No interval is published.

inches of snowfall per month · Snowfall is not snow depth on the ground: NOAA publishes that separately as MLY-SNWD-NORMAL, which is a different dataType and is not used here. Neither is it a depth of water. The water content of this snow is already counted inside the precipitation normals, so adding snowfall to precipitation double-counts, and reading a month's snowfall as if it were that many inches of water substantially overstates the water. The ratio needed to convert it is unpublished for this station and is refused at T02-M06. This station is separated from the Cambridge station by the distance stated at T02-M05, and its figures describe Boston Logan, never Cambridge.

kilometres between two station positions · Both endpoints are station positions published to four decimal places, which bounds each to roughly ten metres, so the separation is good to well under the precision shown. A great-circle distance is a straight-line separation on a sphere; it is not a travel distance and says nothing about what lies between. It is stated only to make the geographic substitution in the snowfall column visible, and it is a distance between two stations, not a distance to any place in Cambridge.

US liquid gallons per square foot per inch of water depth · Rounded to four decimal places, which is far below the hundredth-of-an-inch resolution of the depths it multiplies and is nowhere the limiting term on this page. It assumes liquid water at ordinary temperature and does not model thermal expansion. This is a unit conversion, not a hydrological assumption: it says how large a volume is, never where that volume goes.

square feet · Describes no actual lot, no address and no parcel. The size is not arbitrary: the same lot area appears in the Zoning Ordinance as a threshold, recorded separately at T02-M28, and the district consolidation that made it relevant is recorded at T02-M13. But the decision to model at that size remains an assumption, and every figure derived from it inherits that state.

US liquid gallons per month · This is the volume that ARRIVES on the ground. It is not runoff, not retention and not a load on any pipe, and none of those can be produced from these inputs. Wind, evaporation, interception by vegetation and snow drift are not modelled and would each reduce it. Reported to the nearest hundred gallons because the lot area is an assumption and the depth is a thirty-year average, so finer precision would be false.

US liquid gallons per year · Inherits the single-station caveat of T02-M02 and the assumed lot of T02-M08. It describes a normal year, meaning the average of a thirty-year period that has ended, and not next year. It is water arriving, and says nothing about where any of it goes.

share of lot area, from none to all · A reference point defined by fiat, not a description of any Cambridge lot. Even bare ground does not absorb all the water that lands on it: infiltration is limited by soil type, compaction, slope, antecedent moisture and depth to groundwater, none of which is published for a hypothetical site. So this share, even at its maximum, does not license a retained-volume figure; that limit is recorded separately at T02-M15.

count of outfalls · A citywide permit fact that says nothing about any individual lot. The counts describe what the permit authorises and what is currently open, not how often anything discharges or how much. The City's page states no volume, no frequency and no share of the city served by either kind of system, so neither does this page.

receiving water named by the City for each open outfall · The list describes where each outfall discharges, not how often or how much. It is a permit and infrastructure fact about the city and cannot be attributed to any individual lot, because which system serves a lot is unpublished and recorded as a gap at T02-M19.

percent of required Private open space · This is a fact about a document on a date, and not a statement of what the law requires today. The document itself carries an on-line disclaimer that the print version remains official, and it is current only through an ordinance from 2017. Section 5.22 was replaced wholesale afterwards, which is recorded at T02-M24, and what survives of this requirement is the open gap at T02-M29.

types of Open Space defined for the purpose of the Open Space Ratio · The ordinance states its own intent as revising open space standards to provide greater flexibility by allowing all types of open space to contribute to meeting requirements. Only two of the listed types carry any permeability standard; the others may be met by ground that sheds water. That is why an Open Space Ratio computed under this text is not a measure of how much of a lot can absorb water.

feet of friable permeable material · A standard the ground must meet to be counted as this type of Open Space, not a measurement of any ground. It says nothing about how fast that material accepts water, which is the separate unpublished quantity recorded at T02-M15.

percent of the area counted as Green Area Open Space · A limit on composition within one type of Open Space. It does not follow that the remainder absorbs water at any particular rate, and it says nothing about the other types, which carry no such cap.

feet of walkway width · The stated figure is only the first half of the limit; the operative limit is the smaller of that width and half the width of the area the walkway sits in, so on a narrow area the allowance is smaller than the number shown. The value is carried with the full rule in the formula for that reason.

square feet of total lot area · This applies to Affordable Housing Overlay Projects under Article 11.207 and not universally, and it applies only where the lot directly abuts a Public Open Space of the stated size. It is recorded here because it is one of the places the Zoning Ordinance itself uses this lot area, which is why the scenario at T02-M08 is modelled at that size.

permitted surface character · This single provision is what proves the point of this section: an area may count toward the Open Space Ratio while being hardscaped. It does not say that Private Open Space is usually hardscaped, and City 360 has no measurement of what is actually built.