O-2021-3831 amending Chapter 94 "Floods" of the CoLP Code of Ordinances and Chapter 5 of the PICM

Browse Search

Table 1 Zone Zoning District Name Runoff Maximum Inlet Coefficient “C” Time in Minutes R-1 Low Density Residential 0.50 15 R-2 Mid Density Residential 0.60 15 R-3 High Density Residential 0.80 10 MH Manufactured Housing District 0.55 15 NC Neighborhood Commercial District 0.80 10 GC General Commercial District 0.85 10 BI Business Industrial Park District 0.85 10 LI Light Industrial 0.85 10 HI Heavy Industrial 0.85 10 PUD Planned Unit Development District variable 10 to 15 Miscellaneous Land Uses Land Use Runoff Coefficient “C” Church 0.70 to 0.90 School 0.50 to 0.90 Park 0.30 to 0.70 C. Datum All drainage plans shall be prepared based on North American Vertical Datum of 1988, 2001 adjustment, consistent with National Flood Insurance Program, Flood Insurance Study for the City of La Porte. 5.5 REQUIRED DETENTION Detention will be required to mitigate increase in flows. Minimum detention rates are described in the table below. Minimum storage rate does not apply for single family residential structure and/or accessory buildings proposed on an existing lot. Hydrograph timing may not be used as a substitute for detention when detention is required. 5.5.1 Design Standards for Detention Basins Detention requirements for developments less than 50 acres shall be according to the following table. For developed areas of 10 acres or less, the required volume equals the total development area times the appropriate storage coefficient. For areas greater than 10 acres and less than 50 acres the volume is determined by applying Harris County Flood Control District criteria for small watersheds. Table 2 (Also, See Figure 4) Developed Area Storage Coefficient 0 to 1 acres 0.20 acre ft. / acre 1 to 10 acres 0.55 acre ft. / acre 10 to 50 acres per HCFCD criteria Stormwater Criteria Page 4 of 10