Bulkhead and seawall terms for Mobile Bay owners: a plain glossary

• Deadman: A buried block, beam or plate that a tieback rod anchors to behind the wall.
• Development (flood rules): Any man-made change to land, including buildings, dredging, filling and grading. Mobile City Code Sec. 17-2
• Elevation certificate: A surveyor's form that compares a building's lowest floor with the mapped flood height. In Mobile it is due by the slab pour or before framing at the latest. Mobile flood permit rules
• Existing structure: In ADEM's rules, one begun before October 9, 1985 with every approval in hand. Everything else counts as new. ADEM Rule 335-8-1-.02(ee)
• Fill: Material that raises wetlands or water bottoms. Pilings and pile-supported structures usually do not count, unless ADEM finds they act as fill. ADEM Rule 335-8-1-.02(ii)
• FIRM: The Flood Insurance Rate Map. Mobile County's took effect June 5, 2020, and Baldwin County's April 19, 2019. Mobile County code amendments FEMA Community Status Book
• Floodway: The part of a river channel kept clear to carry floods. Mobile County allows no improvements in a mapped floodway. Mobile County stormwater plan
• Form 166: The older paper joint form for the Corps and ADEM. The Corps now takes requests online and allows Form 166 only in limited cases. Corps Mobile District Its drawings must show mean high and mean low water. Form 166 drawing rules
• Freeboard: Extra height above the base flood elevation. Dauphin Island adds 2 feet. Dauphin Island Ordinance 105
• Gabion: A wire or mesh basket filled with stone. At one Fowl River site, tiered gabion baskets were added to an 85-foot bulkhead. Nature Conservancy Fowl River fact sheet
• Hydrostatic pressure: The push of trapped water behind a wall when the tide drops fast. Weep holes relieve it.

• Letter of Permission: An Army Corps shortcut with a 15-day notice, usually for pile-supported work. Mobile District training handout
• LiMWA: The Limit of Moderate Wave Action, the 1.5-foot breaking-wave line. Mobile City Code Sec. 17-2
• Living shoreline: A shore edge held by marsh plants, oyster reef or rock sills. Nationwide Permit 54 requires a substantial biological part. 2026 NWP 54
• Mean high water (mean high tide): The typical high-tide mark. Alabama owns tidal bottoms waterward of it. ADCNR Rule 220-4-.09(3)(p)
• Mean low water: The average low-tide line, which Form 166 drawings must also show. Form 166 drawing rules
• MHHW: Mean higher high water: the higher of each day's two high tides, averaged over many years. Weather service flood steps at four bay gauges sit 2, 3 and 6 feet above it. NWS coastal flood thresholds
• NAVD88: The height system FEMA's flood maps use. FEMA flood layer, Mobile County
• NFIP: The federal flood insurance program. Its standard dwelling policy skips seawalls, bulkheads, wharves, piers and docks. 44 CFR Part 61, Appendix A(1)
• Nationwide Permit 3 (NWP 3): A Corps permit to fix or rebuild a structure that still works. Storm-damaged structures qualify when repairs begin, or a contract exists, within two years. 2026 NWP 3
• Nationwide Permit 13 (NWP 13): The Corps general permit for shore protection. It covers walls, stone slopes and sills up to 500 feet long. 2026 NWP 13
• Nationwide Permit 54 (NWP 54): The Corps general permit for living shorelines, on shores with low to mid wave energy. 2026 NWP 54

• Outstanding National Resource Water: A special ADEM water-quality designation. It applies to Weeks Bay from Bon Secour Bay to Fish River. ADEM water use rule
• Pile: A post driven into the ground or bay bottom. Pier posts and some wall anchors are piles.
• Pre-construction notification (PCN): Advance notice to the Corps before work begins. NWP 13 requires it for runs over 500 feet or heavy fill. 2026 NWP 13 conditions
• Repetitive loss: Flood damage twice in ten years, averaging at least 25 percent of market value. The City of Mobile counts it toward substantial improvement. Mobile City Code Sec. 17-2
• Request to Impact State Owned Submerged Lands (RTI): State Lands paperwork that starts a Consent of Use, riparian easement or dredge permit. The application costs $100. ADCNR Rule 220-4-.09(4)(e)
• Return wall: A short wall at the end of a bulkhead that turns back into the land. It keeps soil from washing around the end. Also called a wing wall.
• Revetment: A sloped armor layer of rock or concrete along a shore. Mobile County has bid replacing a concrete bulkhead with stone revetment at the Dauphin Island airport. Mobile County airport bids
• Riparian rights: An owner's right to use the water next to their land, including a pier on pilings. ADEM Rule 335-8-1-.05(1)
• Riparian boundary: The side line that splits water frontage between neighbors. Only owner agreement or a court judgment makes it binding. ADCNR Rule 220-4-.09(4)(b)17
• Riprap: Loose stone laid on a slope. State Lands prefers it to a vertical wall where feasible. ADCNR Rule 220-4-.09(4)(b)6

• Scour: Water digging out soil at the foot of a wall. It is why walls get toe protection.
• Shaded X: The 0.2 percent annual chance flood zone. The City of Mobile treats it like the 100-year floodplain for permits. Mobile Land Disturbance Permit Guide
• Sheet pile: Interlocking panels of vinyl, steel, aluminum or concrete driven in a line to form a wall face.
• Special Flood Hazard Area (SFHA): Ground that FEMA maps as high flood risk, including V, A and AE zones. In Mobile, work there needs a flood development permit. Mobile flood development permit
• State submerged lands: Tidal bottoms waterward of mean high tide that Alabama has never conveyed. ADCNR Rule 220-4-.09(3)(p)
• Storm surge: Water pushed ashore by a storm. In Zeta (2020) the Bayou La Batre gauge peaked 6.89 feet above MHHW. NOAA top ten water levels
• Substantial damage or improvement: Repairs or upgrades that reach 50 percent of the building's value before the work or storm. Mobile City Code Sec. 17-2 ADEM uses the same 50 percent line. ADEM Rule 335-8-1-.02(jjj) Dauphin Island counts it over five years. Dauphin Island FAQ
• Tieback: A rod or cable running from the wall face back to a deadman. It stops the wall from leaning out.
• Toe: The buried bottom edge of a wall. Toe protection is rock set at the foot. The 2014 MBNEP guide prices it as an add-on. MBNEP living shorelines guide, 2014
• Upland interest: Proof you control the dry land next to the water, such as a deed, lease or HOA papers. State Lands requires it. ADCNR Rule 220-4-.09(3)(o)
• VE zone: The coastal high-hazard flood zone, where waves add to the water. In Mobile, new buildings must sit landward of mean high tide and keep the space below open. Mobile City Code Sec. 17-29
• Wale (whaler): A horizontal beam along the wall that spreads load across panels and ties them together.
• Weep hole: A small opening that lets water drain from behind a wall. A filter cloth behind it keeps soil from leaking out.
• Zone X: Minimal flood hazard, above the 0.2 percent chance flood. Dauphin Island does not apply its flood standards there. Dauphin Island Ordinance 105

Need more than a definition? See the flood zone guide, the permit guide and the materials guide. Local rules behind several terms appear in the Dauphin Island west end guide and the Bayou La Batre guide.